HVDC TRANSFORMER BUSHING Type PHI 800.1890.4500 …...The transformer bushing is a high voltage DC...

Rev. Description Date Prepared Controlled

0 Emission 10/08/2013 MS GT

IS 2649 GB

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HVDC TRANSFORMER BUSHING

Type PHI 800.1890.4500

Tongli project

OPERATING

AND

MAINTENANCE INSTRUCTIONS

V.le Suzzani, 229 - 20162 Milano (Italy) Tel. 02-66122.1 (ra) - Fax 02-6470906 e-mail: [email protected]

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LIST OF CONTENTS

1 Introduction ................................................................................................................................ 3 2 Safety ........................................................................................................................................ 3

2.1 Safety prescriptions and operative information ................................................................... 4 3 Transport and storage conditions .............................................................................................. 6

3.1 Transport conditions ........................................................................................................... 6 3.2 Lifting conditions ................................................................................................................. 6 3.3 Storage conditions .............................................................................................................. 7

4 Technical characteristics ............................................................................................................ 7 5 Bushing preparation ................................................................................................................. 10

5.1 Bushing unpacking ........................................................................................................... 10 5.2 Bushing controls activities at the arrival ............................................................................ 12 5.3 Tools and equipment ........................................................................................................ 13 5.4 Lifting procedure ............................................................................................................... 15

5.4.1 Lifting tools installation ............................................................................................... 15 5.4.2 Lifting operation ......................................................................................................... 17 5.4.3 Setting the position of the expansion vessels ............................................................ 19 5.4.4 Bushing installation on the stationary support ............................................................ 20

5.5 Bushing installation on the transformer ............................................................................. 22 6 Bushing oil recirculation and filtering. ....................................................................................... 29

6.1 PHI Bushing valves ........................................................................................................... 29 6.2 Oil treatment and filtering equipment ................................................................................ 30

6.2.1 Oil treatment plant ..................................................................................................... 32 6.2.2 Pall filter ..................................................................................................................... 32 6.2.3 Vacuum pump ........................................................................................................... 32 6.2.4 Valve trailer ................................................................................................................ 32

6.3 Bushing oil treatment and filtering process ....................................................................... 33 6.3.1 Oil treatment inside the storage tank ......................................................................... 34 6.3.2 Plant and piping under vacuum ................................................................................. 35 6.3.3 Plant and piping oil filling ........................................................................................... 35 6.3.4 Bushing oil filtering Top to Bottom ............................................................................. 36 6.3.5 Bushing oil filtering Bottom to Top ............................................................................. 38 6.3.6 Bushing internal pressure adjustment ........................................................................ 39 6.3.7 Bushing treatment process conclusion ...................................................................... 40 6.3.8 Final operations ......................................................................................................... 41

7 Transformer turret arrangement and oil parameters ................................................................ 42 8 Gas SF6 characteristics and gas filling instructions ................................................................. 44

8.1 Gas first filling operation and control of alarm and tripping signals ................................... 45 8.2 Gas refilling during the bushing normal operation ............................................................. 46

9 Gas density monitor ................................................................................................................. 46 10 Power factor tap ................................................................................................................... 48 11 Oil pressure gauge ............................................................................................................... 48 12 Voltage divider unit ............................................................................................................... 49 13 Composite insulators maintenance....................................................................................... 50 14 General maintenance plan ................................................................................................... 51 15 Disposal at the end of life ..................................................................................................... 53 Appendix 1 – Bushing outline drawing ............................................................................................ 55 Appendix 2 – Electrical scheme ...................................................................................................... 57 Appendix 3 – Voltage divider .......................................................................................................... 66 Appendix 4 – Gas density monitor Trafag AG ................................................................................. 75 Appendix 5 – Oil pressure gauge .................................................................................................... 82 Appendix 6 - Composite insulators maintenance and repairing ....................................................... 83 Appendix 7 – Bushing installation check list .................................................................................... 93


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1 Introduction These instructions are applicable to the hybrid type HVDC transformer bushings of the PHI series and provide all information relevant to:

Safety aspects.

Transport conditions.

Technical characteristics.

Controls at the arrival and preparation activities.

Lifting and installation operation.

Oil filtering and recirculation.

Gas filling operation.

Service and maintenance plan and procedures.

The PHI bushings are manufactured and tested in compliance with the following standards:

IEC 62199 – 2004 Bushings for DC application.

IEC 60137 - 2003 Insulated bushings for alternating voltages above 1000V.

2 Safety

In this document important safety requirements are highlighted by the word WARNING. Mandatory safety

actions are evidenced by the word OBLIGATION, while important operative instructions are evidenced by the

word NOTE. This manual must be available to the personnel responsible of the installation, operation and maintenance of the bushings. The transformer bushing is a high voltage DC device, filled under pressure with SF6 gas, that realizes the interface between the transformer and the convertor. The arrangement of the bushing allows the passage through the wall of the valve building. The preparation and the installation of the bushing, the oil filtering and treatment process, the gas filling and the periodical maintenance operations must be performed by qualified operators. They have to be trained to operate in accordance with the guidelines described in this instruction manual. Every operator must use the prescribed tools and the prescribed safety devices. Non-compliance with the following procedures and instructions can result in serious and dangerous situations for the personnel and in risks of damages of the equipment and the property and environment pollution.


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Main safety risks related to the bushing handling and its operative conditions are:

Transport and handling of heavy and large parts.

Lifting and moving of heavy and not well balanced goods.

Work operations under the crane and suspended materials.

Work at height. All operation at height must be performed on a suitable certified platform.

Risk of falling down of heavy parts during the installation.

Risks deriving from un-proper balancing of the masses that can cause un-expected rotation during the installation of the bushing on the transformer or on the test turret.

Risks related to the use of un-proper tools or wrong operations. Risks deriving from un-proper installation or operation on the bushing when filled by SF6 gas at rated

filling pressure (risk of explosion).

Environmental risks related to dispersion of SF6 gas in the atmosphere or mineral oil in the environment.

Severe electrical shock risk related to the extremely high voltage DC level of the equipment.

Severe electrical shock risk due to un-proper realization of the bushing grounding connections.

Severe electrical shock risks deriving by the fact that the composite insulator and the other main parts of the bushing remain electrically charged at high voltage for a long period of time after the plant de-energizing and the bushing grounding. Before starting any work on the de-energized bushing, check the discharge by touching all surface of the composite insulator and all other parts of the bushing with an insulated grounding rod which length must be ≥ 3m. During this operation the workers must wear protective insulating gloves and boots and helmets with protective transparent face shield.

2.1 Safety prescriptions and operative information

The following notes are mandatory for personnel involved in transformer bushing installation. All problems detected during the bushing installation must be reported to the Foreman and to Alstom Grid RPV Supervisor.

WARNING: The PHI bushing is a gas pressurized device. Operations on valves, pressure gauges, pipes, protective devices must be performed by qualified operators, with the proper equipment. Foreman and operators have to take careful for handling the pressurized equipment. It is strictly forbidden to move, lift and install equipment that is under pressure. Check through appropriate gauge that the gas side of the bushing is at a pressure less than or equal to 0.125 MPa abs (0.25 bar gauge) before operate on it.

WARNING: Never use damaged or not certified lifting equipment.

WARNING: Lifting equipment must be under a planned maintenance routine. Operators must be qualified and properly trained.

WARNING: Work in quote will be done by trained operators on adequate and certified moving platforms. Workers that will operate in quote must use the prescribed safety devices and in addition they must wear certified safety harnesses.

WARNING: Lifting equipment will be entrusted only to specialized personnel, kept in efficiency and clean. Identification and rating plates must be always present and visible on the equipment. Do not use the equipment when rating plates are missed or unreadable.

WARNING: The equipment is filled with SF6 gas. This gas is not environmentally friend. Always use an appropriate gas filling machine that allows the SF6 recovery. Avoid any dispersion of the gas in the environment.


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WARNING: PHI type bushing is filled and impregnated with mineral oil. Managing oil equipment and processing the oil must be done by qualified operators. Immediately remove oil stains on the shop floor, stairs, elevating platforms and equipment. Fix oil leakages from pipes, equipment and tools in order to prevent pollution and accidents. Provide adequate equipment for oil absorption or oil spills containment. Immediately inform the shop Responsible and the Authorities in case of heavy oil spills. Avoid dispersion in the environment. Oil is a flammable material. Provide adequate firefighting equipment and extinguishers.

OBLIGATION: The use of a safety helmet is mandatory during the use of the lifting equipment and during all bushing installation operation. The helmet must comply with the standard EN 397.

OBLIGATION: During all activities, it is mandatory to use safety gloves complying with the standard EN 388 with performance index not less than 4131.

OBLIGATION: During all activities, it is mandatory to use safety shoes complying with the standard EN 345 with of performance index not less than S2.

OBLIGATION: During works activities carried out at a height greater than 2m it is mandatory to use a safety harness in accordance with the standard EN 361, equipped with a snap-hook in accordance with the standard EN 362, a rope in accordance with the standard EN 354 and a shock absorber in accordance with the standard EN 355.

Tools and pieces of clothes or no-fibre fabric used during the assembly must be clean. The composite insulators sheds are made by silicone that can be mechanically damaged if not properly handled. Protect the insulators with clean plastic foils during the bushing installation and immediately report to Foreman and to Alstom Grid RPV Supervisor any event which could have caused a damage of the composite insulators.


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3 Transport and storage conditions The bushing is shipped in a wooden box suitable for marine transport, designed to provide protection of the bushing in accordance with the specified transport conditions. The complete crate must be lifted, loaded on vehicles and transported with great care to prevent damages of the bushing or its accessories. Stacking of crates is not allowed. An electronic impact recorder is installed on the bushing and it will record all shocks happened during the trip. Additional shock indicators are fixed on the crate walls. Alstom Grid RPV will not respond of any damage due to un-proper operations. Removal or damage of the electronic recorder will cause the interruption of the warranty. The total mass of the bushing packed in its crate is 8800 kg. The crate dimensions are L 1300 cm x W 232 cm x H 220 cm. Centre of gravity and lifting points are painted on the crate walls. 3.1 Transport conditions The bushing can be transported by truck, ship, airplane. The bushing is filled with SF6 gas at a pressure of

0.125 MPa abs (0.25 bar gauge) and mineral oil at a pressure of 1 bar gauge at 20°C (see curve in Figure 21). In order to prevent dangerous movement of the crate during the transport it is responsibility of the transport company to carefully fix it on the vehicle by suitable retain systems like ropes, synthetic pulling bands or any other method. The maximum allowed transport acceleration along the three axis is 3g (29.43 m/s

2). In case of transport by

truck along very bad roads (‘bumpy roads) the speed must be adequately reduced to max 30 km/h. Trucks to be used for road transportation must have a platform of sufficient dimensions to accommodate the overall crate. Crate overhang from any platform and hauling are not allowed. During the transport by road or ship the good must be protected from rain, sea water and other exceptional environment conditions by tarpaulins, not provided by Alstom Grid RPV, suitable to full cover the crate. Sea transportation on the ship main deck is allowed. Transportation in ship hold is preferred. 3.2 Lifting conditions Lifting operation must be done by qualified operators and with certified ropes and equipment.

Lifting points are indicated on the crate and are reinforced by steel plates (see Figure 1). Lifting the crate by fork lift is not allowed.

Figure 1 – Crate lifting arrangement

WARNING: The centre of gravity point of the crate could be not perfectly centred respect the crate geometry. Care must be taken during the lifting and moving operation to prevent dangerous situations, damages or heavy shocks to the good.


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3.3 Storage conditions For short period storage, up to 1 month, the package can be stored outside, just protected by a suitable tarpaulin. The storage area must have a concrete floor made in such a way to ensure a sufficient drainage of water. In this case it is not necessary to remove the electronic impact recorder. For long time period storage, it is necessary that all the crate is placed inside a suitable warehouse, the impact recorder is removed and returned to Alstom Grid RPV and that a periodical check, every six months, of the bushing, the gas pressure and of relevant accessories is activated. If the bushing is installed on the transformer and the complete transformer is stored as spare unit, it is necessary to perform the following actions:

Reduce the gas pressure to the transport pressure value (0.25 bar gauge, 0.125 MPa abs).

Protect the composite insulator with a PE double thickness bag.

Remove the top toroids and wrap them in bubble PE foils then put them in a suitable wooden box to be stored in a covered warehouse.

Record the gas pressure and the oil pressure and the ambient temperature for future reference.

Control and protect the pressure gauges, PF tap and relevant accessories with PE foils and silica gel bags.

Seal all cable passages from the electrical cubicles and protect them with PE foils and silica gel bags.

Activate a periodical check, at least every six months, to check the status of the bushing, the gas pressure that must be ≥ 0.1 bar gauge (= 0.11 MPa abs) and oil pressure.

4 Technical characteristics PHI bushings are based on the hybrid technology. This means that the bushing is based on two different insulation technologies: The first, based on an Oil Impregnated Paper (OIP in the document) grading capacitor, realizes the interface with the transformer. The second, based on a gas insulated section, realizes the interface to the converter plant. The bushing, filled at rated filling pressure with pure SF6 gas, is designed to operate at low temperatures down to -25° C. The Hybrid solution offers the following advantages:

Complete separation between the gas compartment and the transformer turret. Gas leakages to the transformer are not possible and they are detected by suitable pressure gauges at the level of the OIP capacitor section.

Full prevention of transformer oil spills into the valve hall due to the particular bushing structure.

The mineral oil inside the grading capacitor OIP section provides an optimum cooling of the conductor with excellent performances in case of high current ratings and harmonics presence.

The grading capacitor winding is 100% protected from the risk of pollution during the bushing installation on the transformer, as it is fully sealed by special fibreglass barriers.

Next Table 1 reports the bushing main electrical technical characteristics and Table 2 reports the design environmental conditions.

The bushing can be installed on the wall with an angle between 10° and 30° from the horizontal. Figure 2 shows the bushing overall dimensions and outline.

The complete outline drawing is shown in Appendix 1.


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Voltage ratings Bridge rated continuous d.c. voltage Bridge maximum continuous d.c. voltage System rated continuous a.c. voltage System maximum continuous a.c. voltage Bushing rated voltage to U1

800

816

160

165.9

850

kVdc

kVdc

kV line to line

kV line to line

kV

Current rating Rated current Distorted operation harmonics current

4500

See tech spec.

Arms

Short circuit level 37.1 kApk

Rated frequency 50 Hz

Lightning impulse withstand (BIL) 1890 kVpk

Chopped wave 2079 kVpk

Switching impulse dry withstand (SIL) 1680 kVpk

DC 2h voltage test 1433 kVdc

Polarity reversal test 1111 kVdc

Power frequency withstand (1 min) 1036 kVrms

AC PD test (1 hour) 1036 kVrms

RIV at 1.1 Up/√2 ≤2500µV µV

Rated filling pressure @ 20°C 0.65 MPa abs

Table 1 – Bushing electrical characteristics

Indoor conditions: Max. / Min. dry bulb temperatures Max. / Min. relative humidity Max transformer oil temperature

+ 60 / +5

60

85

°C

%

°C

Pollution condition Indoor

Very low

Minimum creepage distance Indoor

17470

mm

Minimum arcing distance Indoor

7658

mm

Seismic condition

Dynamic safety factor

0.2

> 1.67

g

Altitude above sea level (up to) <1000 m

Installation angle 10-30° From horizontal

Table 2 – Environmental conditions


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Figure 2 – Bushing outline


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5 Bushing preparation All operators involved in components unpacking and assembly have to be careful to not damage the objects. During the unpacking operation it is necessary to check that all components supplied by Alstom Grid RPV are available and not damaged during the transportation. All incoming goods must be stored in a covered area and prepared for the installation. At the arrival the crate must be inspected. Any damage of the crate or indication of the visual external shock

recorder (see Figure 3) must be reported to the Foreman and Alstom Grid RPV Supervisor.

Figure 3 – Visual external shock recorder In addition, the bushing is equipped with an electronic shock recorder type Shocklog RD298 or Shocklog 208

(see Figure 4), placed on the bushing top plate. After the arrival on site, this device must be removed and given back to the Alstom Grid Supervisor to be returned to Alstom Grid RPV for data analysis.

Figure 4 – Electronic shock recorders

A detailed control check list is listed in Paragraph 5.2. 5.1 Bushing unpacking The crate is provided with a lid made in three sections. Each section provided with four lifting eyebolts type DIN 582 placed at the four corners. On the crate side walls there are two lines of screws. The upper line of screws are those that hold the lids.

Remove all the upper screws (wrench Nr. 17) that hold the cover to the crate walls (see Figure 5).

Connect the lifting ropes to the eyebolts ropes and remove the three lid sections (see Figure 6).

After the removal of the top lid, remove the crate upper wooden beams that support the top lid (see Figure 7). Remove the plastic foils that cover the bushing but do not remove the PE layer wrapped on the composite insulator. The bushing is locked inside the crate at the level of the central flange and the top flange by locking belts and

bolts (see Figure 8).


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Figure 5 – Lid sections locking screws Figure 6 – Removing the lid sections

Figure 7 – Bushing crate inside view from top

Figure 8 – Top and main flange and locking belts

WARNING: Composite insulator and the oil side fibreglass cone are protected by a PE plastic foils. Remove the protection on the composite insulator only just before the transformer energization. The oil side cone protection must be removed only just before the installation of the bushing on the transformer turret.

WARNING: It is not allowed to step on the composite insulators. The silicone sheds can be seriously damaged.

WARNING: The centre of gravity point is not centred respect the bushing geometry. Care must be taken to compensate the mass unbalancing before and during lifting operations. WARNING: Never wrap ropes (i.e. ‘tie’ lifting method) around the silicone sheds. The composite insulators will be seriously damaged.

Remove these screws

Do not remove these screws

Wooden beams


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5.2 Bushing controls activities at the arrival

Item Control Description Actions on problems

1 Crate inspection Check for evidence of shocks on the crate structure. Check the status of the external shock indicators.

Take pictures of evidences.

In case of deviations notify the Foreman and to Alstom Grid RPV Supervisor.

Continue with the internal inspection.

2 Electronic shock recorder

Check for recorded shocks > 3g In case of deviations notify the Foreman and Alstom Grid RPV Supervisor. Send them the records of the shock recorders.

Continue with the inspection but:

Wait for instructions.

3 Gas filling residual pressure

Check gas pressure: 0.11 MPa abs Gas pressure 0.125 MPa abs

(0.1 bar gauge Gas pressure 0.25 bar gauge)

Record the pressure value.

In case of deviations notify the Foreman and Alstom Grid RPV Supervisor.



4 Oil pressure Check if the oil pressure ≥1 bar gauge

@20°C (see Figure 21). Record the pressure and

the avg. bushing temperature.


Check for oil leakages.



5 Bushing inspection Check the integrity of the oil side cone. Check the bottom terminal and the MultiContact blades. Check the flange and the gas and oil pressure gauges. Check the oil expansion vessels, the oil pipes and all oil valves. Check the wiring and the electrical circuit. Check the integrity of the valves warranty seals and red warning tags. Check for oil leakages. Check the status of the composite insulator and the silicon sheds. Check the top terminal. Check the toroids and relevant accessories.

Take pictures of the various inspected parts.




Table 3 – Bushing controls activities at the arrival


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5.3 Tools and equipment

The tools for the bushing lifting and installation are listed in the next Table 4.

ITEM Description Reference code WLL

[ton.]

Quantity Pictures

1 Lifting device with

centre lift

3828SPEC015 7 1

2 Centering upper plate 3828SPEC013 3 1

3

Wire rope sling with

double master link Φ18

mm Length 12m

3.5

2

Wire rope sling with

aluminium ferrules

Length 12m

4 Anchor shackle 9.5 4

5 Manual chain hoist 5 1

6 Chain sling 2 legs

Length 5m

5.6 1

7 Chain sling 2 legs

Length 3m

2 1

8 Manual chain hoist 1 1

9 Bushing stationary

support

3810SPEC012 1

10 Eye bolt ADA 22 3 2

Table 4 – Lifting and erection tools


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N. 2 cranes with the following technical characteristics:

Single grinder crane.

Crane capacity ≥ 5 t.

Hoist lifting height ≥ 21.5m.

Slow hoisting speed ≤1.3 m/min. Or, as an alternative: N. 2 mobile telescopic crane with the following technical characteristics:

Single crane.

Lifting boom working long ≥ 21.7m.

Hoist lifting height ≥23.9m.

The capacity of the crane must comply with the characteristics indicated in with the following Figure 9. The crane operative working conditions must be within the limits set by the red area.

Figure 9 – Mobile crane working characteristics


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5.4 Lifting procedure This paragraph refers to the bushing removal from the transport crate. All references are to the tool list of

Table 4.

5.4.1 Lifting tools installation

Install the lifting device with centre lift (ITEM 1) on the crane master hook, together with the two wire rope slings (ITEM 3) in their respective working position.

Install the centering upper plate (ITEM 2) on the bushing top flange. If the plate is correctly installed the ‘V’ rounded edge is upward. Lock the three retaining bolts at 310 Nm of torque. Pass both wire rope slings (ITEM 3) through the guiding segments on the centering upper plate (ITEM 2) and firmly lock them inside the guiding segments by the two locking plates and their retaining screws. Warning: Check the installation position of the centering upper plate that must be with

the ‘V’ rounded edge UPWARD with the

Locking plates oriented DOWNWARD. An error in position can cause the fall of the bushing. Check that the retaining bolts are tightened at the proper torque.

Crane Master hook

Lifting device Item 1

Wire rope sling

Item 3

Centering upper plate

Item 2

Locking plates and retaining screws

DOWN

Wire rope sling

Item 3

This side

UP

This side

UP

OK

NO OK

Pulling direction

Pulling direction


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Install on the two bushing lifting hooks on the main flange the two anchor shackles (ITEM 4). Fix both wire ropes sling (ITEM 3) to the anchor shackles (ITEM 4).

Place the chain sling 2 legs length 5m (ITEM 6) on the slave crane hook with the Manual chain hoist WLL 5 Ton. (ITEM 5) in their working position.

Connect the hook of the manual chain hoist (ITEM 5) to the anchor shackle (ITEM 4). If the wire rope ITEM 3 is master link type, see

Table 4, connect the chain hoist directly to master link ring. Similarly, on the other side of the flange connect the hook of the chain sling 2 legs (ITEM 6) to the anchor shackle (ITEM 4) or directly at the master link ring, if the wire rope

(ITEM3) is master link type, see Table 4.

Anchor shackle Item 4

Wire rope sling

Item 3

Crane slave hook

Manual chain hoist 5 Ton

Item 5

Chain sling 2 legs Item 6

Hook from the manual chain

hoist item 5


Wire rope sling

Item 3


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5.4.2 Lifting operation

Gently act on the crane controls and pull the ropes connected to the master hook. Similarly act on the slave hook and pull the ropes and the chains connected with the slave hook. Control that all ropes, chains, hooks, anchor shackles and lifting tools are properly working and that any unexpected part or object remain engaged in the lifting system. Slightly lift the bushing from the side connected to the slave hook and adjust, by the chain hoist (ITEM 5), the correct chain length to ensure the horizontal lifting of the bushing.

Slowly proceed with the lifting operation by carefully acting on both crane hooks (master and slave) in order to keep the bushing horizontal until it is at 4 m above the floor level. Then move the bushing away from the crate in an area free from other objects.


Chain hoist Item 5

~4m


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Carefully continue the lifting operation with the crane master hook only, until the bushing gets to the vertical position. During the lifting operation control that the bottom tail of the bushing remains at a minimum safe distance of 1.5 m from the floor.

Remove the hook of manual hoist (ITEM 5) from the anchor shackle (ITEM 4), or from the master link ring (ITEM 3) if provided (see

Table 4). Similarly on the other side of the flange remove the hook of the chain sling 2 legs (ITEM 6) from the anchor shackle (ITEM 4) or from the master link ring (ITEM 3) if

provided (see Table 4).

Master

hook

≥ 1.5m

Wire rope sling

Item 3

Remove the hook of the

manual hoist Item 5


Wire rope sling

Item 3

Remove the chain sling two

legs Item 6



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5.4.3 Setting the position of the expansion vessels

The vessel must be rotated 90° respect the transport position. The procedure is described here: Remove the upper locking bolts located on the two sides of the vessels frame. These bolts keep the frame blocked in the transport position (wrench Nr. 46). Unlock and release ½ turn the lower bolts on both sides of the vessels frame (wrench Nr. 46).

Place on the slave crane hook the chain hoist WLL 1 Ton.(ITEM 8). Connect to his hook the chain sling 2 legs Length 3m (ITEM 7). Connect the chain sling 2 legs Length 3m (ITEM 7) at the vessels frame.

Remove this screw on both sides of the vessels frame.

Release ½ turn this bolt on both sides of the vessels frame.

1

2

Chain hoist Item 8

Chain sling two legs Item 7



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Lift the vessels frame until it reaches the horizontal position by acting on the chain hoist.

When the vessels frame is in horizontal position, adjust the plane by the chain hoist until it is possible to insert the locking bolts M30 in the frame holes The tightening torque for the all the four M30 bolts is 573 Nm. Remove the chain sling (ITEM 7) from the vessels frame and the chain hoist WLL 1 Ton.(ITEM 8) from the slave crane.

5.4.4 Bushing installation on the stationary support

Place the chain sling 2 legs length 5m (ITEM 6) on the slave crane hook with the Manual chain hoist WLL 5 Ton. (ITEM 5). Re-connect the hook of the chain hoist (ITEM 5) to the anchor shackle (ITEM 4), or to the master link ring (ITEM 3) if provided (see

Table 4), and on the other side the hook of the chain sling 2 legs (ITEM 6) to the second anchor shackle (ITEM 4), or to the master

link ring (ITEM 3) if provided (see Table 4).

Re-connect here the chain sling 2 legs

Item 6

Anchor shackle Item4

Re-connect here the manual chain hoist

Item 5


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Slowly lift the bushing from the side connected at the slave hook and adjust, by the chain hoist (ITEM 5), the correct chain length to ensure the vertical lifting of the bushing. Place the rubber gasket on the stationary support (ITEM 9). Slowly move the bushing on top of stationary support. When the bushing axis is perpendicular to the plane of the stationary support, slowly and simultaneously lower both crane master and slave hooks until the bushing is standing on the stationary support. During this operation check continuously that the bushing axis is coincident with the axis of the stationary support and that the bushing flange holes are aligned with the corresponding holes on the stationary support. Note: It is fundamental to avoid damages of the oil side fibreglass cone. For this reason it is recommended that this part will be protected by PE film during all operation. In case of damages immediately contact the Foreman and Alstom Grid RPV Supervisor.

Fix bushing flange on support or turret flange using M20 screws. The tightening torque for the screw M20 is 413 Nm.


Manual chain hoist

Item 5

Stationary support Item 9

Rubber gasket on stationary

support Item 9


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After the installation of the bushing on the stationary support proceed with the bushing oil recirculation and

filtering (see Chapter 6). 5.5 Bushing installation on the transformer NOTE: Before proceed with this part it is necessary that the oil inside the turret barriers insulating barriers has been processed in accordance to the specifications of the Transformer Manufacturer. Alstom Grid RPV

requirements about the oil conditions and turret processing are described in Chapter 7 and that the bushing

has been filtered and treated as described in Chapter 6. It is under the responsibility of the transformer Manufacturer to guarantee that the interface between the barriers internal electrical shield and the bottom side of the bushing complies with the installation quote

indicated in the bushing Outline drawing (see Figure 10).

Figure 10 – Bottom side of the bushing and interface quote with the barrier shield The complete installation operation must be performed in presence of the transformer Manufacturer Foreman and Alstom Grid RPV Supervisor. The turret must be designed to withstand vacuum and provided with proper filtering valves to allow the oil filling under vacuum and the oil recirculation inside the barrier system After the bushing installation the final oil filling must be done under vacuum. The oil characteristics inside the

barrier system must comply with the data listed in Table 12. NOTE Before to proceed with the installation of the bushing on the transformer, it is necessary that the bushing

oil recirculation and filtering procedure described in Chapter 6 has been completed and that the gas pressure is set at the transport value (0.25 bar gauge, 0.125MPa abs).

Check also that the oil inside the turret barriers complies with the parameters listed in Table 12.

Install the lifting device with centre lift (ITEM 1) on the crane master hook, together with the two wire rope slings (ITEM 3) in their respective working position

Crane Master hook

Lifting device Item 1

Wire rope sling

Item 3

Mandatory quote respect the

metal part of the barrier shield


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Install the centering upper plate (ITEM 2) on the bushing top flange. The rounded edge must be on the side of the expansion vessels. Lock the three retaining bolts at 310 Nm of torque. Warning: Before lifting the bushing, check the position of the centering upper plate that must be with the rounded edge toward the expansion vessels. An error in position can cause the fall of the bushing. Check that the retaining bolts are tightened at the proper torque.

Pass both wire rope slings (ITEM 3) through the guiding segments on the centering upper plate (ITEM 2) and firmly lock them inside the guiding segments by the two locking plates and their retaining screws.

Wire rope sling

Item 3

This side toward the expansion vessels

Locking plates and retaining screws

Locking plate and retaining

screws

OK

NO OK


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Fix the two eye bolts ADA 22 (ITEM 10) to the bushing flange. Disconnect the gas density monitor from its gas tight DILO valve DN 8 (Wrench Nr.30). and block it with plastic strips to prevent that it falls down during the bushing installation.

On the two sides of the bushing main flange connect the two wire ropes slings (ITEM 3) to the anchor shackles (ITEM 4) and the eye bolt ADA 22 (ITEM 10) Gently act on the crane controls and pull the ropes slings connected to the master hook. Check that all parts of the lifting equipment are correctly installed and that the pressure gauge is adequately fixed.

Place the chain sling 2 legs length 5m (ITEM 6) on the slave crane hook with the manual chain hoist WLL 5 Ton. (ITEM 5) in their working position

Connect the hook of the manual chain hoist (ITEM 5) to the master link ring of the wire rope sling (ITEM 3).

DILO DN 8 valve Eye bolt

ADA 22 Item 10

Eye bolt ADA 22 Item 10


Wire rope sling

Item 3

Crane slave hook

Manual chain hoist 5 Ton

Item 5


Hook from the manual chain

hoist item 5


Wire rope sling

Item 3


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Similarly, on the other side of the flange, connect the hook of the chain sling 2 legs (ITEM 6) to the master link ring of the wire rope sling (ITEM 3).

Remove the plastic foil from the bottom resin cone and check that no foreign material can drop into the transformer turret. Carefully clean the resin cone and the bottom terminal with no-fiber fabric and demineralized water.

Slowly lift the bushing from the standing support from the side connected to the master hook. Act on the chain hoist and the slave crane to ensure the masses balancing and the vertical lifting of the bushing. Lift the bushing only when the mass unbalancing is perfectly compensated. Lift by acting on both master and slave cranes. When the bushing is in vertical position, act on the two cranes in order to rotate at the proper inclination angle. Slowly move the bushing on top of transformer turret and then adjust the inclination angle.


Wire rope sling

Item 3



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Check the correct inclination on the transformer side of the bushing flange angle by a Quadranfix inclinometer or by an electronic inclination gauge (not supplied). Control with the same instrument the effective inclination angle of the transformer turret flange and adjust the bushing inclination angle accordingly by acting on the slave crane Concerning the adjustment of the angular position of the bushing respect the turret flange act on the manual chain hoist WLL 5 Ton. (ITEM 5).

When the bushing axis will coincide to the turret axis and the inclination angle is OK, slowly proceed by simultaneously lowering both the master and the slave hooks. By checking continuously that the two axes (turret and bushings) are always coincident, gradually insert the bushing inside the transformer turret. Note: During this operation it is mandatory to continuously check that the bushing cone will remain centred respect the hole in the transformer turret and the CT coils that are normally placed inside the turret. Check that there are no interferences and that no damages or scratches are done on the cone and the metal parts of the oil side of the bushing. In case of damages, immediately contact Alstom Grid RPV Supervisor and the Foreman and stop the operation.

The installation conditions will be slightly different for the factory tests and the on-site condition. In fact for the factory tests it is not necessary to move the oil expansion vessels from the bushing to the transformer tank.

Quadranfix inclinometer

Bushing flange

transformer side

To rotate the bushing act on

the manual chain hoist WLL 5 Ton

Item 5


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Transformer factory tests installation

set-up. If the installation is finalized for the transformer factory tests, it is not necessary to move and install the oil expansion vessels on the transformer tank but keep them on-board of the bushing. Complete the installation of the double toroid on the top.

Fill the bushing with SF6 (see Chapter 8). Complete all relevant activities for the transformer preparation to test.

On site installation set-up. The oil vessel system are installed on a frame that has folded inside the 5m long oil flexible pipe. The pipe is fixed by plastic fasteners to be cut to allow the pipe to be extracted from its support.

Connect the crane hook to the on the top of the vessel frame, remove the 4 x M30 bolts that connects the frame to the bushing and carefully lift the frame. Carefully check that the flexible oil pipe exits from its support on the frame without any interference. Control also that during the positioning of the vessels on the transformer tank the flexible pipe does not remain blocked or interferes with something. Place the vessel frame on its support (see

Figure 11) welded on the transformer tank and fix it with 4 x M12 bolts (torque 83 Nm).

Oil expansion vessels

Folded oil pipe fixed by plastic

fasteners

Plastic fasteners

Oil expansion vessels

supporting frame

Unfolded oil pipe

Max length = 5 m

Vessel fixing plate


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Figure 11 – Plate for oil vessels frame fixing on the transformer

Fix the flexible oil pipe un the supports along the turret with plastic fasteners (recommended the Hellermann-Tyton type KR6/35-W-BK).

Complete the installation of the double toroid on the top of the bushing.

Fill the bushing with SF6 (see Chapter 8). Complete all relevant activities for the transformer preparation.


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6 Bushing oil recirculation and filtering. The bushing oil recirculation and filtering is a mandatory activity to be performed on the bushing before the installation on the transformer. DC Tests on the transformer or the transformer on-site energization can be

done only if the bushing oil characteristics are in line with the parameters listed in Table 9. Energizing the bushing without having re-processed the oil or re-processed with a process not in accordance with the following guidelines, can be dangerous for the integrity of the bushing and of the transformer.

The mineral oil used for the PHI bushings is: Nynas Nytro 4000 A. The same type of oil must be used for the preparation of oil filtering and processing plant and for the eventual re-filling of the bushing. NOTE: The activity described in this chapter is a very special process, consequently it is necessary to carefully follow the instruction described in this document and proceed under the supervision of Alstom Grid RPV Service. In particular:

The oil equipment must be under a planned maintenance routine.

All measuring instruments must be periodically checked and calibrated.

Operators must be qualified and trained on the PHI treatment process. 6.1 PHI Bushing valves The PHI bushing is equipped at the level of the bushing flange of a special valve system that allows:

The oil filling under vacuum

The oil recirculation for filtering and the oil passage during the normal operation.

Depending from their specific function, they are named filtering and by-pass valves (see Figure 12). These valves are located all around the bushing flange (four or six units depending for the bushing size) installed

inside some metallic protrusions on the bushing flange, protected by metal lids (see Figure 13).

Filtering valves block By-pass valve block

Figure 12 – PHI bushing valves

Clo

sed O

pen

By-pass valve

Clo

sed O

pen

Clo

sed O

pen

Clo

sed O

pen

To the pump

To the pump

Filter valve

Filter valve

By-pass valve


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Vacuum pump and oil filling and filtering equipment must be connected to the filtering valves through two ¾” BSP connections placed on the side of each filter valve block. These connections are protected by a

removable cap (see Figure 13). By-pass valves are placed in both type of blocks and are necessary to ensure the proper oil circulation during the normal bushing operation. The by-pass valve blocks are not equipped with the ¾” BSP connections.

Next Table 5 describes the correct valve positions as a function of the specific operative condition on the bushing.

Operative condition Filtering valves By-pass valves

Oil filling and filtering OPEN CLOSED

Bushing normal operation CLOSED OPEN

Table 5 – Filtering and by-pass valve position

Filtering valves block By-pass valve block

Figure 13 – PHI bushing valves and connections arrangement NOTE: After the conclusion of the filtering operation the valves MUST be put in ‘Bushing normal operation’

position (see Table 5). Missing this operation can cause a serious risk of damage of the bushing due to

a lack of oil circulation necessary for the internal cooling of the active part of grading capacitor. After this operation the valve blocks must be closed by their metal lids, the pipes to the pump & filtering plant removed and the connecting taps closed with their removable caps. 6.2 Oil treatment and filtering equipment The oil filtering equipment is made by the following main separate units:

Oil treatment plant.

Pall filter unit.

Valve group trailer.

Oil storage tank

Vacuum pump.

Next Figure 14 shows the main equipment and the piping connections between the oil plant and the bushing.

Metal lid

By-pass valve

Metal lid By-pass valve

Filtering valves

¾” BSP connections

Protective caps


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Figure 14 – PHI bushing oil filtering equipment and piping

Valve group trailer

Pall filter group

Oil treatment plant

Vacuum pump Oil storage tank

BUSHING

VACUUM UNIT

OIL STORAGE TANK


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6.2.1 Oil treatment plant

The main characteristics of the oil treatment plan are listed in the next Table 6:

OIL FLOW FEATURES

Oil flow adjustable Working pressure adjustable Maximum outlet pressure

300 - 1000 l/h 0.08 – 0.4 MPa max. 0.5 MPa

CONNECTIONS

Oil inlet Oil outlet Oil filling

DN 25 (R 1“) DN 25 (R 1“) DN 32 (R 1 ¼“)

OIL TEMPERATURE

T through the heater at different flow rate after one passage

Operating temperature

27 °C @ 1000 l/h 40 °C @ 650 l/h 80 °C @ 300 l/h 40°C - 80°C

VACUUM PUMP

Flow rate Final Pressure

≥50 m3/h

≤10Pa

BUILT IN FILTER:

filter

1 m

SOUND PRESSURE LEVEL (DIN 456335) < 75 dB(A)

Volume (net)

Main tank

Ca. 1000 l.

Table 6 – Oil treatment plant characteristics

6.2.2 Pall filter

The filter is based on Pall cartridges Duofine E. The minimum filtering characteristics are:

Cartridge type Duofine E series DFN02 Outside diameter 10 inches Pressure drop P 0.5 bar @ 1000l/hour

6.2.3 Vacuum pump

The vacuum pump is a two stages 40 m

3/h oil filled air cooled rotary vanes pump with one 250 m

3/h high

vacuum air cooled Roots unit. Residual pressure is ≤ 5 x 10-3 mbar. The unit must be provided with a vacuum gauge Pirani type.

6.2.4 Valve trailer

The valve trailer includes a group of valves and equipment that allow the following operations:

Put under vacuum of all piping from the oil treatment plant to the bushing valves.

Control the oil flow from the oil treatment plant to the bushing and adjust it to the optimum value (700 – 900 l/h).


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Allow the oil flow reversal inside the bushing to ensure the by directional flushing of the oil impregnated

grading capacitor.

Allow the final pressurization of the oil expansion vessels.

Table 7 – Valve trailer arrangement 6.3 Bushing oil treatment and filtering process The bushing oil treatment and filtering includes the following steps:

Oil treatment inside the storage tank.

Plant and piping under vacuum.

Plant and piping oil filling. o Bushing oil filtering Top to Bottom. o Bushing oil filtering Bottom to Top. o Bushing oil filtering Top to Bottom.

Bushing internal pressure adjustment.

Final operations. Next pages describe the complete process. Here below some important information: NOTE: Always check that during the bushing filtering process all filtering valves are in open position and that all by-pass valves are in closed position, unless the filtering process will be not effectively performed.

NOTE: It is fundamental to prevent the draining of the bushing during the filtering process. This is ensured by setting the pressure inside the bushing ≥ 1 bar gauge and continuously controlling the inlet and outlet pressure gauges located on the Valves group trailer. In case of problems or doubts immediately contact Alstom Grid RPV Supervisor.

NOTE: Check that the recirculation process is effectively in progress by controlling the temperature of the bushing bottom terminal. In case of evidence of insufficient recirculation or in case of doubts immediately contact Alstom Grid RPV Supervisor.

NOTE: Carefully follow the procedure described in the following pages. Focus in particular the correct realization of the piping and relevant connections. Always check the correct valves position that must be in line with the following schemes. Mistakes in the process will be extremely dangerous for the integrity of the bushing.

By-pass valve for the oil flow control

DN50 hoses from the oil treatment plant

Oil flow meter

Inlet / outlet bushing pressure

gauges

Valves system for the oil flow

reversal

Vacuum pump

Connecting hoses to the bushing

Shutting valves to the bushing


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6.3.1 Oil treatment inside the storage tank

Figure 15 – Configuration for oil treatment in the storage tank The procedure includes the following steps:

Connect all the equipment as in Figure 15 and set the valves as indicated.

Start the vacuum pump until the overall plant is under vacuum, vacuum level ≤ 0.1 kPa (1 mbar).

Connect the oil drum(s) to the valve ‘A’ and open it.

Fill the oil storage tank with approximately 300 litres of Nynas Nytro 4000A mineral oil.

Close the valve ‘A’ and disconnect the oil drum(s).

Start the oil treatment plant and recirculate the oil inside the treatment plant keeping the oil storage tank under vacuum.

Process the oil by recirculating it until it reaches the parameters shown in Table 8.

Stop the process and close the valves ‘B’ and ‘C’ on the oil storage tank and the valves ‘D’ and ‘E’.

Keep the storage tank under vacuum by keeping the vacuum pump on.

Switch off the oil treatment plant.

Parameter Limit

Water content by Karl Fisher at 20°C ≤ 2 ppm

Breakdown voltage on 2.5 mm gap ≥ 80 kV

Total gas content < 5000 ppm (0.5%)

Power factor at 90°C ≤ 0.005

Resistivity at 30°C ≥15 1012

Ohm x m

Particle content ISO11218 Class 0

Table 8 – Storage tank oil treatment parameters At the end of the treatment process, the oil in the tank must have a temperature ≥ 60 °C and it can be used to

fill the bushing. Treated oil can be maintained under vacuum in the storage tank. Mixing Nynas Nytro 4000A

oil with other types of mineral or synthetic oil is not allowed.

VACUUM UNIT

OIL STORAGE TANK

Green valves: Valve Open

Red valves: Valve Closed

Green equipment: Equipment On

Red equipment: Equipment Off A

C

B

E

DN 50

D


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6.3.2 Plant and piping under vacuum

Figure 16 – Configuration for vacuum of plant and piping The procedure includes the following steps:

Connect the bushing to the DN 32 pipes and keep the bushing filtering valves closed (see Figure 12

and Figure 13).

Connect the equipment as in Figure 16 and set the valves as indicated.

Start the vacuum pump on the valve group trailer ‘VP’ and put all pipes under vacuum, vacuum level ≤0.1 kPa (1 mbar).

6.3.3 Plant and piping oil filling

Figure 17 – Configuration for plant and piping oil filling

BUSHING

VACUUM UNIT

OIL STORAGE TANK

BUSHING

OIL STORAGE TANK




Red equipment: Equipment Off

VP





C

G

H

I

VP D L

F


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The procedure includes the following steps:

Close the two valves across the on the valve group trailer ‘VP’, valves ‘G’ and ‘H’, and switch off the vacuum pump ‘VP’.

Stop the vacuum pump connected to the storage tank and break the vacuum inside the tank via a silica gel breather.

Start the oil treatment plant and gradually open the valve ‘C’ on the storage tank, the valve ‘D’ on the valve & connecting pipes trailer and the valve ‘F’ on the filter trailer. At the end of this operation the

plant configuration will be as in Figure 17.

Check that the oil flows from the storage tank and fills all piping.

Close the valves ‘C’ and ‘D’ and open the valve ‘L’ and allow the circulation of the oil through the overall plant.

6.3.4 Bushing oil filtering Top to Bottom

Figure 18 – Configuration for bushing oil filtering Top to Bottom The procedure includes these preliminary steps to be performed at the beginning of the process:

With the overall plant under recirculation, carefully open all the bushing filtering valves (see Figure 12

and Figure 13).

Let the pressure stabilize inside the bushing and then close all the bushing bypass valves (see Figure

12 and Figure 13).

Set all the plant valves as indicated in Figure 18. Than the process continues with the effective Top to Bottom oil filtering procedure:

Adjust the oil flow by acting on the by-pass valve ‘Bp’. The oil flow must be between 500 – 800 l/h.

Set the pressure inside the bushing until it gets 1 bar gauge on the bushing pressure gauge by acting on the oil return valve ‘M’.

Set the oil temperature on the oil treatment plant to 70±5°C and stabilize it.

Control on the two pressure gauges ‘Pg’ that the pressure is positive and ≥ 1.1 – 1.5 bar gauge. This avoids that the bushing will be drained or that some areas of the bushing will be subject to vacuum.

BUSHING

OIL STORAGE TANK





Bp

M PgM

Pg


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Check that the oil is effectively circulating by controlling the pressure drop between the inlet and outlet piping, by checking that the bushing bottom terminal gets hot. With 70°C inlet and ambient temperature between 15 and 20°C the bottom terminal temperature will get approximately 50°C in 6-8 hours.

The filtering process Top to Bottom is completed when a minimum of 3 oil passes are performed and

the oil meets all the parameters listed in Table 9.

Parameter Limit



Total gas content 200 ppm (0.02%)

Total combustible gases < 10 ppm (0.001%)



Ohm x m


Table 9 – Oil parameters for final oil filling and recirculation

Continue with the Bottom to Top filtering process.

Concerning the ISO 11218 solid contamination limits classes, next Table 10 summarizes the quantities and the size limits for each class:

Classes

Maximum Contamination Limits (particles/100ml)

ISO 11218 > 4

μm(c)

> 6

μm(c)

>14

μm(c)

> 21

μm(c)

> 38

μm(c)

> 70

μm(c)

000 195 76 14 3 1 0

00 390 152 27 5 1 0

0 780 304 54 10 2 0

1 1560 609 109 20 3 1

2 3120 1220 217 39 6 1

3 6250 2430 432 76 11 2

4 12500 4960 864 152 22 4

5 25000 9730 1730 306 45 8

6 50000 19500 3460 6012 90 16

7 100000 38900 6920 1220 180 32

8 200000 77900 13900 2450 360 64

9 400000 156000 27700 4900 720 128

10 800000 311000 55400 9800 1440 256

11 1600000 623000 111000 19600 2880 512

12 3200000 1250000 222000 39200 5760 1024

Table 10 – Solid contamination limits classes according ISO 11218


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6.3.5 Bushing oil filtering Bottom to Top

Figure 19 – Configuration for bushing oil filtering Bottom to Top The procedure includes the following steps:

Reverse the oil flow in the bushing by closing the valves ‘N’ and ‘O’ and opening the valves ‘M’, ‘P’ and

‘Q’. The overall plant set-up will be as in the above Figure 19.

Adjust the oil flow by acting on the by-pass valve ‘Bp’. The oil flow must be between 500 – 800 l/h.

Set the pressure inside the bushing until it gets 1 bar gauge on the bushing pressure gauge by acting on the oil return valve ‘R’.

Set the oil temperature on the oil treatment plant to 70±5°C and stabilize it.

Control on the two pressure gauges ‘Pg’ that the pressure is positive and ≥ 1.1 – 1.5 bar gauge. This avoids that the bushing will be drained or that some areas of the bushing will be subject to vacuum.

Check that the oil is effectively circulating by controlling the pressure drop between the inlet and outlet piping, by checking that the bushing bottom terminal gets hot. With 70°C inlet and ambient temperature between 15 and 20°C the bottom terminal temperature will get approximately 50°C in 6-8 hours.

The filtering process Top to Bottom is completed when a minimum of 3 oil passes are performed and

the oil meets all the parameters listed in the previous Table 9.

At this point it is necessary to perform another oil flow reversal by setting the valves as in Figure 18 then proceed as in Paragraph 6.3.4 for the final Top to Bottom oil filtering. After the completion of the final Top to Bottom oil filtering, perform the final controls of the oil parameters that

must be in line with Table 9 figures and then proceed with the bushing internal pressure adjustment.

BUSHING

OIL STORAGE TANK





Bp

O P

N Q

Pg

Pg

M

R


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6.3.6 Bushing internal pressure adjustment

Figure 20 – Configuration for bushing internal pressure adjustment The procedure includes the following steps:

Set the overall plant as in the above Figure 20.

Measure the temperature of the bushing flange and of the bushing bottom terminal by a contact thermometer and evaluate the average temperature. This is assumed to be the average temperature bushing oil.

Gradually close the valve ‘M’ on the oil return pipe and rise the internal pressure in accordance to the

diagram of Figure 21. The pressure must be measured on the bushing pressure gauge.

If the pressure is OK, simultaneously close the valves ‘R’ and ‘M’ and isolate the bushing from the filtering system.

Open the by-pass valve ‘Bp’, switch off the heating system of the oil treatment machine but not the circulating pump and the de-gasser.

Check for oil leakages from the bushing.

Let the bushing cooling down to ambient temperature, check the final oil pressure and compare the

value with the diagram of Figure 21. In case adjust it by carefully acting on the valves ‘M’ and ‘R’ then close them.

If the final pressure control is OK and no oil leakages are evidenced proceed with the final part of the process.

BUSHING

OIL STORAGE TANK

M

R

Bp






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Figure 21 – Oil pressure vs. average oil temperature

6.3.7 Bushing treatment process conclusion

Figure 22 – Configuration for conclusion of bushing treatment The conclusive operations on the bushing include:

Check that the valves ‘M’ and ‘R’ are accurately closed then switch off the oil treatment machine. The

plant configuration will be like in Figure 22.

On the bushing flange close the all the filtering valves and open all the by-pass valves (see Figure 12

and Figure 13). This is the ‘Bushing normal operation configuration’ (see Table 5).

Proceed with the final operations.

BUSHING

OIL STORAGE TANK

VACUUM UNIT





Temp [°C]

P [bar]


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NOTE: After the conclusion of the filtering process the valves MUST be put in ‘Bushing normal operation’

position (see Table 5). Missing this operation can cause a serious risk of damage of the bushing due to

a lack of oil circulation necessary for the internal cooling of the active part of grading capacitor.

6.3.8 Final operations

Figure 23 – Configuration for plant and hoses oil drainage

Set the configuration of the plant as in Figure 23 – Configuration for plant and hoses oil drainage and switch on the oil treatment plant pump (no heather).

Open the valve ‘E’ and drain all the oil of the plant into the oil storage tank.

Disconnect the DN 32 hoses from the bushing and drain all the oil into the oil storage tank.

Close the valves ‘E’, ‘B’ and ‘I’ switch off the oil treatment plant and the vacuum pump connected to the oil storage tank. The oil in the storage tank will remain under vacuum. Plant arrangement will be as in

Figure 24.

Close all the valve blocks with the proper metal lids and the ¾” BSP connecting taps with their

removable caps (see Figure 13).

Figure 24 – Final configuration

BUSHING

OIL STORAGE TANK

VACUUM UNIT





E

I B

BUSHING

OIL STORAGE TANK

VACUUM UNIT






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7 Transformer turret arrangement and oil parameters This chapter provides guidelines to the Transformer Manufacturer concerning the turret design and preparation of the turret oil processing procedure. Turret design and oil processing procedure are under the responsibility of the Transformer Manufacturer and the concepts illustrated in this part are not mandatory. Required, however, is the achievement of the parameters for the oil inside the pressboard barriers and the turret, listed in

Table 12. The turret shall be designed to withstand the vacuum and it has to be provided with adequate valves to allow the proper bi-directional oil recirculation inside the barrier system. To perform this operation it is suggested that a suitable DN 25 pipe will be welded on the top flange manhole. The length of this pipe should be sufficient to

allow the injection of treated and filtered oil inside the pressboard barriers (see Figure 25).

Example of turret manhole with filtering pipe Example of internal DN 25 filtering pipe

Figure 25 – Example of turret manhole with internal DN 25 filtering pipe

Next Figure 26 shows an example of turret arrangement during the treatment operation and relevant oil flows that can be realized with this arrangement.

Figure 26 – Transformer turret arrangement during filling and filtering operation

Top valve

DN 25 internal pipe

Connection to the Buchholz relay

Oil Flow

Turret manhole

DN 25 filtering pipe

Bottom valve

Transformer turret

CT arrangement

PB barriers

HVDC transformer

lead

A

A

B

C

D Vacuum

Oil sampling valve


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The oil treatment plant to be used for the process should have the following characteristics:

Be provided with 1µm filter with ceramic type cartridges. Paper type is not acceptable;

able to recirculate under vacuum;

sufficient heating power to ensure an oil temperature in the test tank ≥70°C;

oil flow ≥ 4000 l/hour;

possibility to reverse the oil flow in the turret without disconnecting the pipes. The recommended procedure includes the following steps:

Vacuum in the turret o Apply vacuum to the turret via the transformer oil conservator and the Buchholtz relay pipe. o Vacuum level ≤ 0.1 kPa (1 mbar). o Vacuum time at vacuum level: ≥ 48 h.

Oil filling under vacuum from bottom

o Minimum oil filling characteristics as in Table 11. No air has to remain trapped inside the

transformer turret.

Parameter Limit

Water content by Karl Fisher ≤ 3 ppm

Breakdown voltage on 2.5 mm gap > 70 kV


Inlet oil temperature ≥70°C

Table 11 – Minimum oil filling parameters for turret filling

o Minimum impregnation time under vacuum: ≥ 12 h.

Recirculation of the internal side of the pressboard barriers from the DN25 internal pipe o Oil treatment plant connected to point ‘A’ to bottom valve ‘B’. o Recirculation steps: ‘A’’B’, ‘B’’A’, ‘A’’B’ (Top to Bottom, Bottom to Top, Top to Bottom). o Min. number of oil passes of total oil volume for each recirculation step: 3.

o Temperature of the oil at the return pipe: ≥70°C. o Recirculate the internal part of the barriers until parameters are in line with Table 12 data.

Recirculation of the outer side of the pressboard barriers o Oil treatment plant connected to valve ‘B’ and ‘C’. o Recirculation steps: ‘B’’C’, ‘C’’B’ (Bottom to Top, Top to Bottom). o Min. number of oil passes of total oil volume for each recirculation step: 1.5.

o Temperature of the oil at the return pipe: ≥70°C. o Recirculate the outer side of the barriers until parameters are in line with Table 12 data.

Bushing installation o Break the vacuum in the turret via a silica gel breather. o Drain from valve ‘B’ an oil volume corresponding to the bushing oil side volume (approximately

500 dm3 for the PHI 820 kV).

o Connect the valve ‘C’ to a dry air equipment and circulate the air inside the turret. o Open the turret manhole by taking care that any foreign material will drop inside the turret.

o Install the bushing in accordance to the procedure at Paragraph 5.5.

Final filling and oil recirculation o Connect the oil treatment machine to the valves ‘B’ and ‘C’. o Apply vacuum to the turret via the Buchholtz relay pipe. o Vacuum level in the turret ≤ 0.1 kPa (1 mbar). o Vacuum time @ vacuum level: ≥ 3 h.

o Fill the turret from valve ‘B’ with treated oil as in Table 11. No air has to remain trapped

inside the transformer turret. o Recirculate from valve ‘C’ to valve ‘B’ (Top to Bottom) for a minimum of 2 passes of total oil

volume, until the oil temperature on the return pipe is ≥ 70°C and the parameters are in line

with Table 12 data.


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o Complete the filling operation of the transformer and apply the standing time defined for the

transformer procedure.

o Check the oil characteristics inside the transformer turret that must be in line with Table 12

data (see also Table 10 for the ISO 11218 solid contamination limits classes).

Parameter Limit



Total gas content < 5000 ppm (0.5%)



Ohm x m


Table 12 – Oil parameters for turret final oil filling and recirculation

NOTE: Fibre count readings may be adversely affected by a number of issues and thus the following aspects points need to be ensured:

The vacuum pump is operating effectively.

The vacuum and pressure values are balanced in the system.

There are no extreme temperature influences.

The velocity of pumping does not cause turbulent flow or bubble evolution.

The sampling point is not in a position subjected to vacuum or turbulent flow which may damage the on line equipment and is reasonably close to the output of the tank circulation system.

Bottle sampling is NOT recommended as the reading may well be higher and the Class 00 criteria difficult to achieve.

8 Gas SF6 characteristics and gas filling instructions

The SF6 gas to be used to fill the bushing must comply with the data shown in the following Table 13. This table shows the limits stated by Alstom Grid RPV specification and the characteristics of a premium Supplier:

Characteristics Unit Alstom Grid RPV limits

Premium Supplier’s limits

Min SF6 % by weight ≥99.9% ≥99.993%

Air ppm by weight ≤500 ppm ≤50 ppm

CF4 ppm by weight ≤500 ppm ≤10 ppm

H2O ppm by weight ≤15 ppm ≤0.65 ppm

Mineral oil ppm by weight ≤10 ppm ≤1 ppm

Total acidity expressed in HF ppm by weight ≤0.3 ppm ≤0.3 ppm

Hydrolizable fluorides in terms of HF ppm by weight ≤1 ppm ≤1 ppm

Table 13 - Characteristics of new SF6 gas according Alstom Grid RPV and premium Supplier The minimum requirement is that the characteristics have to be in accordance with the data listed in the Alstom Grid RPV limits column. The gas filling must be performed with an equipment that prevents dispersion of the SF6 gas in the

atmosphere. As an example, next Figure 27 shows a gas plant manufactured by the German company DILO GmbH.


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Figure 27 – Vacuum filling gas plant DILO NOTE: This bushing has to be operated with pure SF6. In case of need of replacement of SF6 gas with a mixture SF6 N2, before to proceed, please contact Alstom Grid RPV for instructions and approval.

WARNING: The following safety notes are mandatory.

The bushing can be filled at the rated filling pressure of 0.65 MPa abs (5.5 bar gauge @ 20°C), only when installed on the transformer ready for the electrical tests or placed inside valve hall wall.

If, for any reason, the bushing has to be removed from the transformer turret, it is mandatory to reduce the gas pressure to 0.125 MPa abs (0.25 bar gauge) before proceeding with the operation.

If the transformer is stored with the bushings installed, the gas pressure must be reduced to 0.125 MPa abs (0.25 bar gauge) and periodically checked.

All gas filling and gas recovering operations must be performed by a gas plant device (example a DILO machine).

8.1 Gas first filling operation and control of alarm and tripping signals The bushing is shipped in slight overpressure of SF6 gas. If the pressure is positive proceed in the operation as follows, unless contact Alstom Grid Supervisor for additional instructions.

Connect the gas plant to the DILO filling valve on the bushing flange.

Gradually increase the gas pressure up to 0.2 MPa abs (1 bar gauge). Pressure must be directly measured on the gas density monitors installed on the bushing flange.

Check all the gas seals for leakages with a suitable SF6 leak-meter device. In case of significant leakages stop the activities and contact Alstom Grid Supervisor.

If the bushing does not show any leakage gradually increase the pressure at the rated filling pressure value of 0.65 MPa (5.5 bar gauge). The pressure must be directly measured on the compensated gas density monitors installed on the bushing flange.

During the pressure rising, check the functionality of the Tripping (0.53 MPa abs), Alarm 2 (0.55 MPa abs) and Alarm 1 (0.58 MPa abs) contacts and record the respective operating pressures on the bushing check list. In case of malfunction, check the wiring and inform Alstom Grid Supervisor.

During the alarm / tripping functionality test, record on the bushing check list the readings on the two gas density monitors.

Keep the bushing at the rated filling pressure for 4 hours, the purpose of this standing time is to allow the gas temperature stabilization, then make the final adjustment of the gas pressure.

Disconnect the gas plant from the DILO filling valve located on the bushing flange. The gas density monitors installed on the wall bushing are fully thermally compensated devices that indicate the pressure independently from the effective gas temperature. Whatever the temperature of the gas, the instrument indicates a pressure equivalent to an average gas temperature of 20°C. This condition is related with the gas density inside the bushing.


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8.2 Gas refilling during the bushing normal operation The bushing is a fully sealed unit and its leakage rate is <0.5% x year. Anyway, after many years of operation it could be necessary to refill it. The refilling operation has to be done within 7 – 10 days after Alarm 1 intervention and it is mandatory to perform it within 1 – 2 days after the Alarm 2 intervention. Gas refilling can be done from the DILO type valve located on the bushing flange by a gas plant or a SF6 bottle, equipped with the appropriate pressure reduction equipment and DILO connecting plug (contact DILO GmbH for information about filling set equipment for direct bottle filling). The filling procedure is here below described:

Connect the gas filling equipment (gas plant or SF6 system for direct filling from gas bottles) to the filling valve of the bushing flange.

Gradually and slowly increase the gas pressure up to the rated filling pressure value of 0.65 MPa abs @20°C (5.5 bar gauge). Pressure must be directly measured on the temperature compensated pressure gauge installed on the gas filling station.

Stop the gas filling equipment and shut the bottle valves.

Disconnect the filling equipment from the gas filling station DILO valve.

NOTE: In case of use of the DILO machine, check that the machine set-up is for gas filling and that the connecting pipe is full of SF6 before connecting to the gas filling station DILO valve. In the case of direct filling from the bottle, check that the bottle is effectively charged with SF6, that the gas quantity is sufficient for the re-filling, the pressure reduction unit and the pipe are compatible with the DILO filling system and all equipment is specific for SF6 filling application and certified for a safe use. Also in this case, before to connect the equipment to the gas filling station, check that the connecting pipe is effectively filled by SF6 gas.

CAUTION: The gas re-filling operation MUST be performed with the bushing de-energized and grounded. Safety prescriptions of Chapter 2 must be followed.

WARNING: The refilling action must be performed by qualified operators. The risk is that a wrong operation can drain the gas from the bushing with possibility of plant tripping and equipment damages if the gas leakage will be excessive.

WARNING: Always use equipment certified for SF6 gas. This will avoid mistakes, safety issues and risk for the environment and the equipment.

9 Gas density monitor The bushing is equipped with two gas density monitors manufactured by Trafag AG. The two instruments are different as one is a normal gas density monitor, while the other is equipped with an electronic pressure transducer 6-20 mA for remote indication (hybrid type) and a low pressure indicator, useful for controls of the transport pressure. These devices ensure a great accuracy in the measurement, as they are based on the continuous and direct comparison between the gas density inside the bushing and the gas density of a built-in reference chamber filled with the same gas. This system is different and more accurate respect to the normal instruments that estimate the gas density through a pressure measurement corrected by a bimetal element that takes into account the ambient temperature.

The next Figure 28 shows the instruments and the graduated scale.


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Gas density monitor

Hybrid type gas density

monitor with low pressure

indicator

Instruments scale

Figure 28 – Trafag gas density monitors The indication on the scale is expressed in MPa abs, referred to a gas temperature of 20°C. This means that the instrument convert the gas density into a value of pressure referred to 20°C, independently for the effective temperature of the gas. With this system the instrument reading practically does not change with the gas temperature, that is a function of the bushing loading condition and ambient temperature. Changing of reading during the bushing normal operation is an indication of gas leakages or malfunction of the instrument. Each gas monitoring device is equipped with three change-over micro switches that provide signals for alarm

and tripping signals. Table 14 shows the micro switches purpose and the pressure set up (see Appendix 2 for the exact contacts arrangement of each gas monitoring device).

Micro switch Description Pressure set up

[MPa abs]

Alarm 1 Low pressure level 1 0.58

Alarm 2 Low pressure level 2

Minimum operating pressure 0.55

Tripping Too low pressure for operation 0.53

Table 14 – Alarm and tripping micro switches set-up The instruments are installed on DILO valves for easy disassembly without the need to completely remove the gas from the bushing. In addition, the electrical cables of all devices are wired in a junction box provided with DIN type terminal

boards for easy assembly and maintenance (see Appendix 2).

Additional information about the gas density monitor devices are in illustrated in Appendix 4.

NOTE: Due to the instrument principle of operation, the replacement of bushing gas from SF6 to a gas mixture SF6 N2 is not allowed without replacing the gas density monitors with the proper type. In this case contact Alstom Grid RPV for support, instructions and approval.

NOTE: The instrument equipped with the electronic sensor cannot be subject to the 2 kV 1’ on the terminals of

the electronic sensor (terminals marked + - and relevant wiring at the junction box terminals X10 30 and 31) The application of such voltage to ground will cause an immediate failure of the instrument.


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10 Power factor tap The bushing is equipped with one PF tap. This tap is used for capacitance, tan-delta and partial discharge measurements during the tests and in operation. In operation it must be accurately closed with its screwed metal cap that ensures also the grounding connection.

Figure 29 – Power factor tap To the PF tap it is possible to connect the voltage divider for the valve operation controlling system (see

Chapter 12). WARNING: PF tap MUST be accurately closed with its cap or connected to the voltage divider unit. Missing the cap is dangerous and it will cause an electrical discharge at bushing energizing.

11 Oil pressure gauge

The bushing is equipped with an oil pressure gauge (see Figure 30) provided with electrical contact to detect the following events:

Low oil pressure, related to the possibility of an oil leakage from the oil impregnated paper section.

High oil pressure, related to an internal fault in the oil impregnated paper section or a gas leakage from the gas section of the bushing.

Figure 30 – Oil pressure gauge

The instrument is equipped with 4 micro-switches that provide alarm / tripping signals. Table 15 shows the micro switches purpose and the pressure set up.

Screwed cap

Clip type contact

PF tap insulator

Contact pin


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Micro switch Description Pressure set up

[bar gauge] [MPa gauge]

Low pressure Tripping

Too low pressure for operation 0.2 0.02

Low pressure Alarm

Low pressure related to low oil level

0.4 0.04

High pressure Alarm

Overpressure inside the OIP section

2.6 0.26

High pressure Tripping

Too high pressure inside the OIP section for operation

2.8 0.28

Table 15 – Alarm and tripping micro switches set-up The pressure gauge is installed on a ball type valve for easy replacement in case on need and all electrical

cables are wired in the junction box provided with DIN type terminal boards (see Appendix 2).

Additional information about the oil pressure gauge device are in illustrated in Appendix 5.

12 Voltage divider unit The unit is provided by a capacitive voltage divider for an indirect measurement of the AC component of the transformer voltage through the PF tap. The main characteristics are:

Parameter Description Value

V1L Rated line to line voltage 160.7 kV

V1Lmax Maximum line to line voltage 165.9 kV

V2L Rated line to line secondary

voltage at V1L 110 V

Accuracy Max voltage ratio error at RL 3%

RL Min resistive load 1 MOhm

Table 16 – Alarm and tripping micro switches set-up The unit is made by two separate parts. The first is the adapter to the PF tap that includes also 2 protection surge arrestors and the electrical box that includes all other electric components of the divider. The two parts are connected by a BNC cable. The divider is a passive unit so the loading capacity is limited. It must be used in conjunction with a suitable electronic amplifier. The accuracy class is guaranteed for resistive loads ≥ 1 MOhm.

More information on the voltage divider are illustrated in Appendix 3. WARNING: The divider is not designed for the test voltages. In addition the presence of surge arrestors can cause electric disturbances during the tests. For this reason it is necessary to disconnect it during the electrical tests of the bushing or the complete transformer. The PF tap must be closed with its own metallic cap or directly connected to the test instruments.


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13 Composite insulators maintenance Composite insulators manufactured by qualified and experienced suppliers, require very limited maintenance. The silicone used for the sheds is highly hydrophobic and it has the property to transfer this characteristic to the pollution layer. Cleaning of the composite insulator is necessary only in case of heavy contamination. Due to the installation on the bushing that is inside the valve hall, cleaning by washing is not possible. In this case cleaning can be done only manually by using a sponge and clean water. The composite must be accurately rinsed and then dried with a clean cotton fabric pieces. In case of heavy contaminated areas, use a

solution of isopropyl alcohol, rinse with water and dry with clean cotton fabric pieces. Appendix 6 describes the composite insulator cleaning procedure of the composite manufacturer.

In case of accidental damage of silicone sheds, the repairing procedure is illustrated in Appendix 6. The composite manufacturer can provide a repairing kit and also a technical support for the repairing activity. WARNING: Severe electrical shock risks deriving by the fact that the composite insulator and the other main parts of the bushing remain electrically charged at high voltage for a long period of time (hours) after the plant de-energization and the bushing grounding. Before starting any work on the de-energized bushing, check the discharge by touching all surface of the composite insulators and all other parts of the bushing with an insulated grounding rod which length must be ≥ 3m. Operators must wear protective insulating gloves and boots and helmet with protective transparent face shield.

WARNING: Bushing cleaning must be performed with the bushing de-energized.

WARNING: Inspection of the bushing with the plant energized must be done by qualified technicians fully in accordance with the safety rules specific for the access to the valve hall.

Useful indications about the composite insulator maintenance plan main actions are shown in Table 17.

It is recommended to perform all Table 17 listed actions, as a reference starting point, at the plant start-up. The periodical controls have to check variances or significant anomalies respect to this reference status.

Time base

Vis

ual

insp

ecti

on

UV

cam

era

an

d

infr

are

d

exam

inati

on

1 Year X

When plant is off X

Table 17 – Composite insulator maintenance plan

Visual inspection: Carefully check that the composite insulators sheds do not show any mechanical damages and significant tracking or erosion due to electrical stress. Visually evaluate also the pollution status and identify the areas of concentrated contamination. Take note of the position of the areas of evidences, to be carefully analysed and taken under control during future inspections. In case of evidence of incipient erosion / tracking, plan an immediate cleaning action.


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UV camera and infrared examination: Scan all the surface of the composite insulators with an UV camera to identify possible areas of intense UV emissions on the sheds, on the toroids and the incoming cables. To perform this test, the camera must be properly set in order to avoid false signals and background noise. In addition, an infrared scan on the line terminal and the incoming cables can reveal incipient hot spots phenomenon that can evolve into a serious damage on the electrical connection and then of the bushing itself. In case of significant variation of the UV and IR emission, plan the following actions: UV emission: Immediate cleaning action on the interested part, in the meanwhile control all electrical connections. IR emission: Immediate control of all electrical connections. WARNING: This operation is performed with the plant energized. All specific safety procedures related to the operation inside the valve hall must be accurately followed. The activity must be done by qualified and trained technicians. All precautions must be followed to prevent severe accidents.

14 General maintenance plan

The general maintenance plan is described in the next Table 18.

Component Time base Description Notes

Composite insulators See Chapter 13 Inspection and maintenance See Chapter 13

Gas SF6 When plant is off Check the pressure and the operation of the density monitors

Visual control of pressure at bushing density meters

Bushing oil When plant is off Check the pressure Control if the pressure is in line with the diagram of

Figure 21.

Oil leakages When plant is off

Check for the presence of oil leakages from the bushing flange, along the oil pipe and on the relevant fitting and expansion vessels

Contact Alstom Grid RPV in case of evidence of oil leakages from the bushing parts or accessories.

Toroids When plant is off Clean the surface and check for scratches or deformation. Check the fixing bolts to the flanges.

Anticipate the controls if UV camera reveals corona inception.

Current terminals When plant is off

Check for evidence of hot spots. Check the terminals and tighten the connecting bolts to the bushing flange. Check the cable clamps and the bolting to the terminal.

Anticipate the controls if IR camera reveals hot spots. Contact Alstom Grid RPV in case of evidence of hot spots during the inspection.


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Component Time base Description Notes

Grounding terminals on the bushing flange

When plant is off

Check for evidence of hot spots. Check the connection integrity and the bolt locking. Verify the effectiveness of the grounding.

Contact Alstom Grid RPV in case of evidence of hot spots.

Power factors taps (only if the bushing is not equipped with the voltage divider)

When plant is off

Open the taps and clean inside. Check the internal spring loaded contact and clean it. Perform a Megger 1 kV insulation test Rins > 1 MOhm. Carefully close and tighten the cap.

WARNING: PF tap cap MUST be accurately closed. Missing the cap could be dangerous and it can cause an electrical discharge at bushing energization.

Voltage divider When plant is off

Check that the PF adapter, the BNC cable and the divider box does not show any evidence of electrical discharge. Control the status of the components and the electrical connections inside the box.

Contact Alstom Grid RPV in case of evidence of problems.

Bushing oil Every 2 years, when the plant is off

Perform an oil DGA in accordance to IEC 61464.

Contact Alstom Grid RPV in case of evidence of problems and provide all DGA data.

Gas density monitors and oil pressure gauge

5 years Check calibration and operation of micro switches.

Check the effective and correct operation of the alarms & tripping signal chain from the instruments to the substation systems.

Bushing overall gas leakage

5 years

Check with SF6 leak-meter device all the flanges joints and the DILO valves.

Anticipate the control if the leakage rate is excessive and gas re-filling is frequent. Identify the leakage areas. In case of frequent re-filling, plan for the replacement of the bushing and contact Alstom Grid RPV.

Gas quality 5 years Check the moisture content in accordance to IEC 60480.

Regenerate / replace the gas if moisture exceeds the limits stated in the standard (>25 mg/kg).

Table 18 – Bushing general maintenance plan


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15 Disposal at the end of life At the end of the bushing operative life all parts can be recycled or disposed as follows:

Part Material Action SF6 gas SF6 Remove by DILO machine, recycle or thermo-destruction

Bushing oil Mineral Oil Remove and recycle or thermo-destruction

Grading capacitor Oil impregnated paper and aluminum foils and tube

Dispose or thermo-destruction

Main central flanges Aluminum Dismount and recycle.

Central conductors Aluminum Dismount and recycle

Top flange Aluminum Dismount and recycle

Top electric terminals Copper silvered Dismount and recycle

Toroids Aluminum Dismount and recycle

Internal electrostatic shields Aluminum Dismount and recycle

SF6 and oil side cones Fibreglass Dismount and dispose

Aluminum Recycle the aluminum

Composite insulators with flanges Fibreglass Dispose or thermo-destruction

Silicone Dispose or thermo-destruction

Aluminum Dismount and recycle

Electrical wiring Aluminum Recycle

Copper Recycle

Plastic Dispose or thermo-destruction

Galvanized steel Recycle

DILO valves Stainless steel Recycle

Oil expansion vessels Steel Recycle

Oil expansion vessel supports, piping and valves

Stainless steel Recycle

Gas density monitors and oil pressure gauges

Various Dispose or recycle as electronic products

Gaskets EPDM rubber, Viton Recycle or dispose or thermo-destruction

Table 19 – Bushing end of life management


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List of appendices

Appendix 1 – Bushing outline drawing.

Appendix 2 – Electrical scheme.

Appendix 3 – Voltage divider.

Appendix 4 – Gas density monitor Trafag AG.

Appendix 5 – Oil pressure gauge

Appendix 6 – Composite insulators maintenance and repairing.

Appendix 7 - Bushing installation check list.


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Appendix 1 – Bushing outline drawing


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Appendix 2 – Electrical scheme


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Appendix 3 – Voltage divider


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Appendix 4 – Gas density monitor Trafag AG


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Appendix 5 – Oil pressure gauge


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Appendix 6 - Composite insulators maintenance and repairing


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Appendix 7 – Bushing installation check list Bushing type:__________________________________________________________

Bushing Serial Number:__________________________________________________

Substation:____________________________________________________________

Item Description Activity Limits / recording Action on problems Date Signature

1 Controls at the arrival

Check the wooden crate status. No great damages outside. Take pictures and inform Alstom Grid RPV

Check the external visual impact recorder(s). No intervention of the devices. Take pictures and inform Alstom Grid RPV

Open the crate and inspect packaging and goods inside. No visible damages on goods. Take pictures and inform Alstom Grid RPV

Check the pressure of the gas inside the bushing.

Check gas pressure:

0.11 MPa abs Gas pressure 0.125 MPa abs

(0.1 bar gauge Gas pressure 0.25 bar gauge)

Contact Alstom Grid RPV

Check the composite insulator status, the top terminals and the relevant accessories. No damages. Take pictures and inform Alstom Grid RPV

Check that the oil pressure is ≥1 bar @20°C, record the bushing avg. temperature and that there are not oil leakages on bushing.

Pressure and temperature recording

At gauge M1: _________ bar gauge

tavg: _________ °C

In case of pressure not in line with the diagram pressure / temperature or evidence of oil leakages contact Alstom Grid RPV

Check the bushing instruments and the status of the electric wiring. No damages. Contact Alstom Grid RPV.

2 Impact recorder Remove the impact recorder and ship it to Alstom Grid RPV. --- ---

3 Bushing lifting from the crate and installation on the stationary support

Control the status the lifting equipment and relevant tools and control the crane status and characteristics.

See instruction manual Do not proceed with the operation if tools are damaged or not available.

Install the lifting equipment on the bushing in accordance to the instruction manual at

Paragraph 5.4. See instruction manual ---

Position the stationary support in a proper position and check its stability. --- ---

Check the proper position of the centering upper plate on the bushing flange, of the locking torque and control the proper installation of the wire rope.

See instruction manual Retaining bolts M24 torque = 310 Nm

---

Lift the bushing from the crate in accordance to the instruction manual. See instruction manual ---

Raise the expansion vessels in accordance to the instruction manual. See instruction manual ---

Install the bushing on the stationary support and lock it with M20 screws. See instruction manual. Retaining bolts M20 torque = 413 Nm

---

4 Bushing oil filtering and recirculation

Control the status and the characteristics of the overall equipment. See instruction manual ---

Check the filter cartridges. Replace them if they are not clean ---

Connect the filtering plant to the bushing. See instruction manual ---

Check the oil type for filtering. Oil type: ____________________________ If different from the bushing oil (Nynas Nytro 4000 A) stop and contact Alstom Grid RPV

Check the oil characteristics after the treatment in the storage tank (see instruction

manual Table 8).

Oil final characteristics: Water content by KF at 20°C: ________ ppm Breakdown voltage on 2.5 mm gap: ___ kV Total gas content: _________________ ppm Power factor at 90°C: ______________

Resistivity at 30°C: ________________ x m Particle content ISO class: __________

Repeat the process until parameters will be OK.

Complete the preparation of the treatment and filtering plant See instruction manual ---


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4 (cont)

Bushing oil filtering and recirculation (cont.)

Proceed with the Top to Bottom filtering in accordance to the instruction manual until oil

parameters are in line with Table 9 data. Check the effective oil circulation by controlling the temperature of the bottom terminal and the oil side cone.

Oil characteristics after Top to Bottom filtering: Water content by KF at 20°C: ________ ppm Breakdown voltage on 2.5 mm gap: ___ kV Total gas content: _________________ ppm Power factor at 90°C: ______________


In case of lack of circulation contact Alstom Grid RPV

Reverse the oil flow and proceed with the Bottom to Top filtering in accordance to the

instruction manual until oil parameters are in line with Table 9 data. Check the effective oil circulation by controlling the temperature of the bottom terminal and the oil side cone.

Oil characteristics after Bottom to Top filtering: Water content by KF at 20°C: ________ ppm Breakdown voltage on 2.5 mm gap: ___ kV Total gas content: _________________ ppm Power factor at 90°C: ______________



Reverse the oil flow and proceed with the final Top to Bottom in accordance to the

instruction manual until oil parameters are in line with Table 9 data. Check the effective oil circulation by controlling the temperature of the bottom terminal and the oil side cone.

Final oil characteristics after filtering & recirculation: Water content by KF at 20°C: ________ ppm Breakdown voltage on 2.5 mm gap: ___ kV Total gas content: _________________ ppm Power factor at 90°C: ______________



Measure the temperature of the bushing flange and of the bottom terminal and evaluate the average temperature.

Temperature measurement: Bushing central flange: ___________ °C Bushing bottom contact: ___________ °C Tavg: ___________ °C

---

Calibrate the oil pressure in the bushing as a function of the oil average temperature

Tavg. See instruction manual Figure 21.

Oil pressure at Tavg: Oil pressure: _________________ bar gauge

---

Let the bushing to cool down to ambient temperature and check the oil pressure at

ambient temperature. See instruction manual Figure 21.

Oil pressure: Oil pressure: _________________ bar gauge Tamb: _________________ °C

---

Set all filtering and by-pass valves as for Bushing normal operation.

See instruction manual Figure 12, Figure 13 and Table 5. Check that the valves to the expansion vessels are Open.

Valves positions final check:

Filtering valves Closed:

By-pass valves Open:

Expansion vessels valves Open:

---

Close the valve blocks and apply the protective caps on the ¾” BSP connections. See instruction manual ---

Perform the final operations on the filtering and treatment plant. See instruction manual ---


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5 Transformer turret treatment data

Check that the transformer turret has been processed in accordance with the Transformer Manufacturer procedure and that oil parameters inside the barriers are in

line with Table 12 data.



If parameters are not OK stop bushing installation activities and proceed with a new

treatment of the transformer turret.

Inform Alstom Grid RPV.

6 Bushing installation on the transformer turret from the stationary support

Control the status the lifting equipment and relevant tools and control the crane status and characteristics.

See instruction manual Do not proceed with the operation if tools are damaged or not available.

Install the lifting equipment on the bushing in accordance to the instruction manual at

Paragraph 5.5. See instruction manual ---

Check the proper position of the centering upper plate on the bushing flange, of the locking torque and control the proper installation of the wire rope.

Release the retaining bolts M24 from the stationary support.

---

Control the bottom terminal, the MC blades and the small centering resin cone --- Contact Alstom Grid RPV

Remove the plastic protection from the bottom cone and accurately clean it with a no-fiber fabric cloth.

Remove any foreign material from cone, bottom terminal and flange

---

Lift the bushing from the stationary support and move it close to the transformer See instruction manual ---

Incline the bushing in accordance to the installation conditions with oil expansion vessels upward).

See instruction manual ---

Check the inclination angle of the bushing and of the transformer turret See instruction manual ---

Drain the oil from the transformer turret (min 500 l) See instruction manual ---

Open the turret manhole providing that any foreign material drops inside See instruction manual ---

Insert the bushing into the turret

Check that the cone will not interfere with the metal parts of the turret and the CT and that the oil side cone is not damaged. No damages on the cone are allowed.

In case of damages on the cone surface: - Contact Alstom Grid RPV. - Remove the bushing from the turret and

put it on the stationary support. - Close the transformer turret with the

manhole. - Stop the activities and wait for instructions.

Control the effectiveness of the electrical plug-in contact with the transformer leads Check to be done in accordance with the Transformer manufacturer instructions.

Remove the bushing and control the MC blades on the bottom terminal

Fix the bushing flange on the transformer turret Lock the bolts with the torque prescibed by the Transformer Manufacturer

---

Connect the grounding cables to the bushing flange Min. total cross section 300 mm2 ---

Install the expansion vessels on the transformer tank and fix the flexible tube with the plastic fasteners

See instruction manual ---

Check the correct position of the valves from the bushing to the expansion vessels and control the warranty seals

Valves in Open position Open the valves and seal them with the

warranty lead seal (Alstom Grid RPV supervisor).

Remove all lifting devices --- ---


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7 Final filling and oil recirculation Put the turret under vacuum and fill with treated oil.

Recirculate the turret until oil parameters are in line with Table 12 data.



No air has to remain trapped inside the

transformer turret.

---

8 Gas filling

Check the gas parameters from gas certificates. See instruction manual Do not fill with gas if gas is not OK.

Connect the gas hose to the bushing DILO type valve. See instruction manual ---

Start filling operation. Stop at 1 bar gauge (0.2 MPa abs) ---

Check for leakage with the gas leak-meter device. Check all bushing flanges and connections and also all the gas filling station

Contact Alstom Grid RPV.

Increase the gas pressure until the Tripping contacts operates (0.53 MPa abs). Gas pressure (B1/B2)=______/_____MPa abs NO OK: 1) Check the wiring. 2) Reduce the gas pressure and repeat the

full test sequence. 3) Inform Alstom Grid RPV

Increase the gas pressure until Alarm 2 contact operates (0.55 MPa abs). Gas pressure (B1/B2)=______/_____MPa abs

Increase the gas pressure until Alarm 1 contact operates (0.58 MPa abs). Gas pressure (B1/B2)=______/_____MPa abs

Increase the gas pressure at the rated filling value (0.65 MPa). Wait 4 hours stabilize and record the pressure values.

Pressure recording

At gas monitor B1: _________ MPa abs

At gas monitor B2: _________ MPa abs

---

9 Check PF tap and voltage divider Check that the PF tap is firmly closed or that the adapter is installed and wired to the divider unit.

See instruction manual

Do not energize the bushing if the PF tap is

open or it is not connected to the voltage

divider unit

---

10 Remove composite insulator plastic foils Remove all plastic protective foils from both composite insulators when the bushing is installed and the transformer is inside the valve room.

--- ---

11 Top shield installation Install the top shield bushing when the transformer is inside the valve room. ---

HVDC TRANSFORMER BUSHING Type PHI 800.1890.4500 …...The transformer bushing is a high voltage DC...

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Transcript of HVDC TRANSFORMER BUSHING Type PHI 800.1890.4500 …...The transformer bushing is a high voltage DC...