OPERATING INSTRUCTIONS FOR CAST RESIN TRANSFORMERS · 2019. 12. 26. · 3 OPERATING INSTRUCTIONS...

OPERATING INSTRUCTIONSFOR CAST RESIN TRANSFORMERS

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TABLE OF CONTENTS

1. Safety notices ........................................................................................................................................................................3

2. Reference standards ..............................................................................................................................................................5

3. Nameplate .............................................................................................................................................................................5

4. Transport, receipt and storage ................................................................................................................................................64.1 Lifting the transformer ........................................................................................................................................................64.2 Moving the transformer ..................................................................................................................................................... 74.3 Storing the transformer ...................................................................................................................................................... 7

5. Installation ........................................................................................................................................................................... 85.1 Installation examples .........................................................................................................................................................85.1.1 Installation with housing .................................................................................................................................................85.1.2 Installation without housing ............................................................................................................................................85.2 Connections on the low voltage side ..................................................................................................................................95.3 Connections on the high voltage side .................................................................................................................................95.4 Tightening torque for electrical and mechanical connections ............................................................................................ 105.5 Positioning ...................................................................................................................................................................... 105.6 Ventilation .......................................................................................................................................................................115.7 Protection against overvoltages ....................................................................................................................................... 125.8 Temperature monitoring systems ..................................................................................................................................... 12

6. Commissioning .................................................................................................................................................................... 136.1 Earth connection of the transformer ..................................................................................................................................136.2 HV and LV connections .....................................................................................................................................................136.3 Cleaning ...........................................................................................................................................................................136.4 Switching for voltage setting ............................................................................................................................................ 146.5 Measurement of windings earth resistance .......................................................................................................................156.6 Energising ........................................................................................................................................................................15

7. Maintenance ........................................................................................................................................................................ 167.1 Table on the main maintenance operations ...................................................................................................................... 167.2 Guide for trouble-shooting ................................................................................................................................................177.3 Customer Service ..............................................................................................................................................................17

8. Additional information ......................................................................................................................................................... 188.1 Exploded diagram of the cast resin transformer ................................................................................................................ 18

9. Notes ................................................................................................................................................................................... 19

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OPERATING INSTRUCTIONS FOR CAST RESIN TRANSFORMERS

1. SAFETY NOTICES

The supplier is not liable for damages incurred as a result of failure to observe the following information or the improper use of the transformers described here. All work related with this transformer may only be performed by qualified electricians. The transformer may only be operated by qualified electricians! This guide does not cover all the details or possible variations of the entire series of connections, installation and possible operations. For further information or to solve specific problems that are not included in this guide, please contact the manufacturer. This guide must always be at hand in the vicinity of the transformer. Every operator is obliged to read this guide carefully.

A cast resin transformer is an electrical machine. It must be installed, protected and used in compliance with the existing national and international standards and regulations. Improper installation and use may cause risks of electric shock or fire.

Please read this installation manually carefully before lifting, moving or putting the transformer into operation.

All work must be performed when the transformer is not energised.

Do not get close to the transformer before having connected the windings to earth.

Before performing any work, make sure that the transformer cannot be put under voltage accidentally.

Do not put the transformer into operation before having connected the core to earth.

Do not put the transformer into operation before having carefully and completely inspected it (e.g. for forgotten tools).

Do not access the transformer’s operation area or remove the protection devices when the transformer is under voltage.

All transformers generate a magnetic field. For this reason, people with pacemakers should not get closer than 3 m to a transformer that is in operation.

This transformer must be installed according to the installation instructions by a skilled and qualified electrician. All Ruhstrat transformers may only be repaired in the plant by qualified technicians approved by Ruhstrat. All claims for compensation and warranty are rendered invalid in case of repairs by unauthorised persons.

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1. LV connections

2. Lifting eyebolts

3. Rating plate

4. HV connections

5. Core in three columns

6. LV windings

7. HV windings

8. Off-load tapping links

9. Carriage with bi-directional rollers

10. Terminal box (IP54)

11. Temperature monitoring

12. Delta connection

13. Structure, armatures and carriage

14. Earthing terminals

15. Pulling holes

16. HV epoxy resin insulation

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11

12

13

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6

7

8

9

4

3

2

1

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2. REFERENCE STANDARDS■ IEC 60076-11 – Power transformers – Part 11: Dry-type

transformer.■ IEC 60076-1 – Power transformers – Part 1: General.■ IEC 60076-2 – Power transformers – Part 2: Temperature

rise.■ IEC 60076-3 – Power transformers – Part 3: Insulation levels,

dielectric tests and external clearances in air.■ IEC 60076-5 – Power transformers – Part 5: Ability to

withstand short circuit.■ IEC 60076-10 – Power transformers – Part 10: Determination

of sound levels.■ IEC 60085 – Electrical insulation – Thermal evaluation and

designation.■ IEC 60270 – High-voltage test techniques – Partial discharge

measurements.■ IEC 60529 – Degrees of protection provided by enclosures

(IP code).

3. NAMEPLATEA nameplate showing nominal values and the serial number is attached to each transformer.

3.1 Conditions for the correct operation of the transformer■ Observance of all the instructions in this manual.■ Operation of the transformer in accordance with the rating

plate data.■ Earth connection of the transformer with the correct

terminals.■ Protection of the transformer against chemical agents,

pollution, atmospheric pollution, sun radiation as well as vegetation and animals that could influence smooth operation.

■ Protection of the transformer against mechanical damages during installation and operation.

■ Protection against overvoltages.

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4. TRANSPORT, RECEIPT AND STORAGEDuring transport, the transformers must be properly fixed as shown in the drawings. Make sure that the retaining straps do not touch or damage the HV and LV connections.

NO YES

Carefully examine the transformer upon receipt.

In particular, check the terminals and the HV and LV connections. Make sure the HV windings are not scratched and/or torn and are centred in relation to the LV windings.

Check the integrity of the protection enclosure (if present). In case of dirt, foreign particles, moisture or water, the transformer must be cleaned and dried.

Check that the data on the nameplate correspond to data indicated on the supplied shipping documents and test reports of the transformer.Check that each transformer is provided with the contractually specified accessories.

Record any discrepancies and transport damages on the documents and immediately notify the forwarding agent and manufacturer.

4.1 Lifting the transformerUse all 4 eye bolts to lift the transformer. The angle between the ropes may not exceed 60°.

Avoid jerky movements to the transformer.

If the transformer is supplied with an enclosure, remove the lid before attaching the ropes.

NOYES With housing

Only move the transformer in vertical position.

The transport of the transformer is only permitted according to the descriptions listed below.

Make sure that the transformer does not tilt during lifting and take into account the transformer’s centre of gravity.

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4.2 Moving the transformerOnly the lower eyelets may be used to move the transformer.

Anchoring points for horizontal movement

YES

Do not move the transformer by applying force on the windings or their connections.

Movement can be made only in two directions, according to the rollers' orientation.

It is recommended to avoid moving the transformer more than 10 m on the rollers.

4.3 Storing the transformerIf the transformer is not installed immediately (with or without enclosure), it must be protected against water, dust, humidity and sunlight.

The packaging supplied with the transformer must not be removed for storage.

The temperature during storage and installation must not be below -25°C.

After a long storage period at very low temperatures or in an environment with high humidity, the transformer must be dried before being put into operation.

Fig.: Stored transformers with protective film

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5. INSTALLATIONDuring installation, always protect the windings to avoid external parts such as bolts, washers, tools, cable parts, etc. falling into the windings and impacting the insulation capability of the transformer.

Cast resin transformers are designed for indoor installations, in a site protected from direct sunlight, in clean and dry environments, without risk of water penetration. The standard installation must be performed under the following conditions:

1. At a sea level height not above 1000 m

2. The temperature of the cooling air may not exceed the following values:

a. 20 °C annual average value b. 30 °C warmest month average c. 40 °C maximum

3. Conformity with all other operating conditions as per IEC 60076-11 standard.

The accident prevention regulations must be observed during installation.

5.1 Installation examplesThe HV and LV cables can be connected both from the bottom and the top. Here are some examples:

5.1.1 Installation with housing

5.1.2 Installation without housingThe LV and OV connections must comply with the clearances as specified in the following table. This applies to both the windings of the transformer and the Delta connections. All connected cables must always be supported to avoid mechanical stress on the terminals.

Voltage (kV) D (mm)

≤ 12 ≥ 125

≤ 17.5 ≥ 170

≤ 24 ≥ 225

≤ 36 ≥ 320

HV cables entry

Phase sequence Work to be performed

from the top U - V - W None

from the bottom

V - W - U Move the bolts from the top to the bottom terminals

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The HV cables must not be routed through the Delta connection.

5.2 Connections on the low voltage sideThe LV terminals are positioned on the upper part of the transformer. In the standard version, these are made of aluminium.

We recommend making the cable connection with tinned-copper (DIN 46235) cable terminals, connecting one or two cables in each hole.

In the case of LV connections with busbar, it is necessary to use flexible connections to mechanically isolate the transformer from the busbars. If the LV terminals are connected to busbars with untreated copper, we recommend the use of Cupal plates. The plates are optionally available on request.

5.3 Connections on the high voltage sideThe HV terminals are brass bolts.

If the cables are connected to the bottom bolts, the top bolts must be mounted in the bottom end parts. Observe the phase sequence as described on page 8.

Do not replace the brass bolts with bolts of a different material, as this would affect the connection.

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5.4 Tightening torque for electrical and mechanical connections

Tighten screws and bolts of electrical and mechanical connections in accordance with the values in the following table:

Electrical connections (Nm)

Mechanicalconnections

Screw/nut Steel Brass (Nm) (mm)

M 6 10 - 15 5 - 10 20 10

M 8 30 - 40 10 - 15 35 13

M 10 50 - 60 20 - 30 45 17

M 12 60 - 70 40 - 50 60 19

M 14 90 - 100 60 - 70 100 22

M 16 120 - 130 80 - 90 150 24

M 18 - - 200 27

M 20 - - 270 30

M 22 - - 360 32

M 24 - - 460 36

We recommend retightening the connections with the same tightening torque after a few hours of operation in order to compensate for any adjustments.

Always use two tools when tightening to avoid deformation or damage.

5.5 PositioningThe IP00 cast resin transformer does not ensure protection against contact.

It is strictly prohibited to touch the cast HV coils while the transformer is in operation.

For this reason, the transformer must always be installed in an enclosure, inside a cage or in a room which is only accessible via lockable doors.

Inside this transformer room, the transformer must be installed in accordance with its relevant insulation class. The minimum clearances (transformer wall) indicated in the table must be observed.

kV A (mm) B (mm) C (mm)

≤ 12 ≥ 125 ≥ 60 (*)

≤ 17.5 ≥ 170 ≥ 80 (*)

≤ 24 ≥ 225 ≥ 120 (*)

≤ 36 ≥ 320 ≥ 200 (*)

* C=B except when there is no voltage switch present on the LV side. Otherwise C=A.

In order to prevent horizontal movement of the transformer, the mounting direction of the wheels can be modified on one side.

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5.6 VentilationThe losses generated in the rated operation must be dissipated from the room in which the transformer is installed. The ambient temperature indicated on the data sheet must not be exceeded.

Therefore, the room must be equipped with an S opening at the bottom part, to ensure an adequate flow of fresh air. In addition, an S-opening must be provided on the opposite wall at the top in order to extract the hot air.

The size of the opening is determined from the following formulas for an annual average temperature of 20°C.

S = 0.185 × (DL / √H) inlet opening (fresh air) in m2S' = S × 1.15 outlet (hot exhaust air) in m2

TL = sum of no-load losses and short-circuit losses expressed in W according to the nameplate.

H = height between both openings in m

Transformers directly fixed to the floor without rollers must be installed elevated from the floor to ensure air circulation.

Transformers supplied with protective housing must be installed at a distance of 0.2 m from the surrounding walls in order to allow for air circulation.

If the room is undersized or poorly ventilated, we recommend the installation of a forced ventilation system which ensures a flow rate of 3.5 - 4 m3 of air per minute for each kW of losses.

If the transformer is equipped with cross-flow fans, please note that their service life of the fans is approximately 20,000 hours and they need to be replaced thereafter. We recommend switching them on when the temperature exceeds 90 °C and switching them off when the temperature falls below 80 °C.

S fresh air

S’ hot exhaust air

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5.7 Protection against overvoltagesTo protect the transformer from overvoltages, adequate surge arresters must be installed. These need to have technical properties which depend on the level of insulation of the transformer and on the MV distribution system.

Optional surge arresters are available.

5.8 Temperature monitoring systemsIn the standard version, the transformers are equipped with PTC or Pt100 temperature sensors.

The wiring diagrams are included in the terminal box of the sensors.

The recommended settings for the temperature monitoring is indicated in the table.

Insulation classWarning Switch-off

°C °C

180 °C (H) 140 155

155 °C (F) 130 140

130 °C (B) 110 120

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6. COMMISSIONINGThe manufacturer is not liable for the installation of the transformer. Before the transformer is put into operation, the following checks must be performed.

6.1 Earth connection of the transformerThe PE conductor must be connected to the corresponding earth bolt of the transformer. The size of the earth conductor must be calculated in accordance with the fault current and applicable regulations.

In any case, the PE conductor must have the following cross-section:

■ Copper: 16 mm2

■ Aluminium: 35 mm2

■ Steel: 50 mm2

The prescribed isolation distances from current-carrying parts must be observed for the installation.

Fig. Earth bolt

6.2 HV and LV connections

1. Ensure that the windings are not moved and that the screws are correctly positioned in the coil holder block. The rubber must be slightly depressed.

2. Check the connecting cables between the HV terminals and LV terminals and tighten them with the specified tightening torques.

3. Check that temperature control system is in working order.

Optional: If the transformer is equipped with cross-flow fans, check the direction of rotation of the fans and the air flow.

6.3 CleaningThe transformer must be checked and cleaned in case of contamination, in intervals specified by the operator. For new installations and in case of contamination that cannot be estimated, a check after a maximum of 6 months is recommended. For low degrees of contamination, the cleaning interval can be lengthened. In case of high contamination, the cleaning interval must be shortened and actions must be taken to reduce the contamination.

Take special care when cleaning the cooling channels. If necessary, the cooling channels and coil surfaces can be cleaned in a de-energised state using compressed air, vacuum cleaners and cleaning cloths.

The lack of the need for maintenance is restricted if the transformer is equipped with a forced cooling system or additional cooling with appropriate cross-flow fans. When inspecting the transformer rooms, always ensure that the inlet and outlet openings are clear to allow for proper air circulation.

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WARNING: Prior to maintenance work, the transformer must be disconnected from the power supply and the safety notices must be observed.

6.4 Switching for voltage regulationMains voltage fluctuations can be compensated for by means of switching tabs. The switchover must be performed in a de-energised state.

The transformers are supplied as standard with 5 voltage sockets: ±5% in steps of 2.5%.

The wiring diagram for the tappings is indicated on the nameplate.

It is important to adjust the switching tabs on all three phases of the primary voltage so they are in the same position and are connected to the same sockets.

Different settings can result in permanent damage to the transformer due to an unbalanced power flow.

In the standard version, the switching tabs are positioned on the front side of the HV windings.

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6.5 Measurement of the earthing resistance of the windingsThe insulation resistance is measured with an insulation measuring device. The HV and OV terminals must be disconnected from the power supply during measurement. The measured values should be approximately as follows:

5000 V for 60 s: HV terminal / LV terminal to earth >= 20 MΩ2500 V for 60 s: HV terminal / LV terminal to earth >= 10 MΩ2500 V for 60 s: HV terminal / LV terminal to earth >= 10 MΩ

If the measured values are significantly lower, dry the transformer and, if necessary, contact the after sales department.

6.6 EnergisingBefore switching on, any tools, foreign objects, dust, etc. must be removed from the transformer and windings.

Once all described instructions have been followed, the cast resin transformer may be switched on.

We recommend switching on the transformer in “idle mode”.

For more information about the inrush current, please contact or ask the manufacturer.

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7. MAINTENANCEIn normal operating conditions, cast resin transformers do not require specific maintenance except for that indicated in the following table. All the operations performed must be recorded in order to be submitted to the manufacturer on request.

7.1 Table for the main maintenance operations

ItemCheck activity /

maintenance workCheck frequency Auxiliaries to be used Expected results

1

Correct operation of the temperature sensors (PT100/PTC) and temperature evaluation devices

Every six months and after exceptional events

Industrial dryer for simulated heating of the temperature sensors

Simulated alarm and shutdown at the evaluation device

Observe the operating instructions of the evaluation device!

2Cleaning of the windings: Remove dust, dirt, grease and foreign objects

Yearly. If the environment is particularly dusty, the check must be performed more frequently

Clean, dry compressed air, maximum pressure 3 bar and dry rags

Cleaned cooling channels in all winding areas

3Removal of condensation and moisture

After a prolonged standstill of the transformer, strong temperature fluctuations

Idle mode until a temperature of 80 °C is achieved in the iron core

Dried cooling channels

4

Check bolts and nuts of the HV and LV terminals including all electrical connections

Yearly and after exceptional events.

Torque wrenchTightening torque according to point 5.4

5Measurement of insulation resistance to earth of the windings

After a standstill of the transformer.

Insulation measuring instrument (megger)

See section 6.5

6Check that the LV and HV windings are perfectly aligned

After exceptional events such as electrical or mechanical events

Roller dimension, visual inspection

Uniform centring of both winding parts

7Tighten the upper coil holder blocks

Yearly and/or after exceptional events.

Torque wrenchTightening torque between 20 and 40 Nm

8Tighten the nuts and bolts of the mechanical parts and fixing to the floor

Yearly and after exceptional events.

Torque wrenchTightening torque according to the table in point 5.4

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7.2. Guide to the identification and fixing of errors

Item Problem Possible causes Corrective action

1 Excess temperature at a windingIrregular load distribution

Check position of connections and balance load distribution

Faulty sensor or evaluation device Replace the faulty element

2 General overheatingHigh ambient temperature, insufficient room ventilation, damaged fans

Reduce room temperature, replace faulty fans, clean the cooling channels

3 Overheating in the coreEddy currents, insulation fault in the horizontal clamping bolts

Call Customer Service

4

Abnormal noise Primary voltage too high

Check that the voltage on the off-load secondary windings is lower or equal to the one indicated on the nameplate. Change the switching tabs as per point 6.4

Humming noise Resonances of the magnetostriction; fixing elements of the core too lose

Place shock absorbers under the rollers; tighten loose fixing elements according to point 5.4

5Temperature control devices trigger;Faulty sensor or evaluation device

Faulty unit or sensor Replace the faulty element

Higher current ratings Reduce load; install cross-flow fans

Cooling air does not circulate See point 5.6 and point 6.3.

6Triggering of the protective device on the HV side when the transformer is switched on

Inrush current too highAdjust and set protective device to inrush current

7.3 Customer ServiceFor more information or accessories please call Customer Service at +49 551 820 830 - 0 or send an email to [email protected]. Please indicate the serial number of the transformer as specified on the nameplate.

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1. Magnetic core

2. Core head

3. Vertical tension members

4. Top bracket

5. Bottom bracket

6. Under carriage

7. LV windings

8. HV connections

9. HV windings

10. HV connections

11. Top coil holder blocks

12. Bottom coil holder blocks

13. HV delta connection

14. LV connection insulators

15. Insulator supports

16. Lifting eyebolts

17. Interchangeable rollers

18. Earth bolt

19. Terminal box for temperature sensors

20. Nameplate

8. ADDITIONAL INFORMATION

8.1 Exploded diagram of the cast resin transformer

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20

10

814

3

13

17

216

15

411

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1

7

12

18

56

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9. NOTES

2019 © RPT Ruhstrat Power Technology GmbH I 05-2019 | 01

All rights reserved. All texts, images and graphics are subject to copyright and other intellectual property rights. Content may only be used by prior agreement with RPT Ruhstrat Power Technology GmbH. All information, descriptions and illustrations are subject to technical alterations,

particularly with regard to the continuing development of our products to the current state of the art. No specific notice will be given of modifications to information, descriptions or illustrations. Individual errors are not excluded. Technical features may vary from country to country.

ELT-BA-001-en-1018

RPT Ruhstrat Power Technology GmbHHeinestraße 12 · 37120 Bovenden · Germany

Tel.: +49 55 93 9 37 22-0 · E-Mail: [email protected]

www.ruhstrat.com

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OPERATING INSTRUCTIONS FOR CAST RESIN TRANSFORMERS · 2019. 12. 26. · 3 OPERATING INSTRUCTIONS...

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Transcript of OPERATING INSTRUCTIONS FOR CAST RESIN TRANSFORMERS · 2019. 12. 26. · 3 OPERATING INSTRUCTIONS...