HIGH VOLTAGE INSTRUMENT TRANSFORMERS DDB/DFK DDN/DFN

USER MANUAL

CONTENTSPRELIMINARY CONSIDERATIONS

INTRODUCTION

TRANSPORT AND HANDLING

INSTALLATION

INSPECTION AND MONITORING QUICK

TROUBLESHOOTING GUIDE

ANNEX I

ANNEX II

ANNEX III

HIGH VOLTAGE INSTRUMENT TRANSFORMERS

DDB/DFKDDN/DFN

1 High Voltage Instrument Transformers | DDB/DFK/DDN/DFN

User manual

OBSERVATIONS/

Keep the instruction manual in a safe and accessible place to ensure that any operation or maintenance task can be performed quickly and easily when necessary.

For safety reasons, only qualifi ed staff can use this equipment.

Read the instruction manual and other documentation before the equipment’s installation, commissioning and maintenance.

Become familiar with all equipment information and safety precautions before using the equipment and during its operation.

Always use the equipment within the guidelines indicated in the instruction manual and in other relevant documents.

In order to prevent malfunctions, carry out proper controls and maintenance.

Do not use or handle the equipment in a manner contrary to what is expressly stated in this manual, do not modify the equipment with parts from other manufacturers. This behavior can lead to damage to the equipment and/or personal injury.

ARTECHE is not liable for accidents due to causes unrelated to our guidelines.

In the event of equipment malfunction or any other type of problem, communicate it immediately to the corresponding ARTECHE department, providing the following information:

› Evaluation of contents and the product’s nameplate (name, serial number, type and date of manufacture).

› Description of the problem (as detailed as possible, including the situation immediately before and after the problem occurred) and supporting photos or videos.

If you have any questions, please contact www.arteche.com. › Europe, Africa & Middle East:

[email protected]

› Asia (except Middle East) and Oceania:[email protected]

› North America, Central America and the Caribbean:[email protected]

› South America:[email protected]

PRELIMINARY CONSIDERATIONS

DANGER/

CAUTION

Indicates that improper use o handling may result in physical

damage to the equipment, serious injury or even death

SAFETY PRECAUTIONS/

For safety reasons, only qualifi ed personnel can carry out maintenance and commissioning or operation.

Read the instruction manual and other documents before using the equipment. Become acquainted with every aspect of the equipment and its safety precautions before using it.

Do not use, handle or modify the equipment in a way that is not expressly stated in these operating instructions and do not use or modify the equipment with parts from other manufacturers.

The safety precautions used in this manual are indicated by the following message:

Depending on the situation, mishandling can have serious repercussions, even when “Caution” is indicated in this instruction manual. Strictly observe all security measures.

These safety precautions are the manufacturer’s suggestions to ensure the safety of the equipment.

Users are requested to establish security measures so as to maintain safety and the equipment operating in accordance with various standards and requirements.

ARTECHE will not be liable for accidents caused by not carrying out the safety measures.

ENVIRONMENTAL CONSIDERATIONS/

Disposal considerations:

Disposal or recycling will be carried out in accordance with current legislation. Oil and impregnated products shall be disposed of through an authorized manager in authorized plants. They can be incinerated in suitable plants, respecting local regulations. The oil is free of PCBs and chlorinated products. More information on the oil safety data sheet. The metals are recyclable (copper, steel, aluminum, silver, etc.).

Measures to be taken in the event of an oil spillage:

Prevent the oil from spreading or getting into the sewage system, ditches or rivers by using sand, absorbents or other appropriate barriers. Collect the oil with an absorbent material and send it to appropriate containers for disposal, in accordance with local legislation. Oil is not easily biodegradable. It contains components with bioaccumulation potential.

2High Voltage Instrument Transformers | DDB/DFK/DDN/DFN

User manual

INTRODUCTION

FOREWORD/

This manual describes the construction, installation, commissioning and monitoring for safe use of a high-voltage instrument transformer insulated by oil-paper.

SCOPE OF APPLICATION/

The manual applies to the following transformers:

› Capacitive Voltage Transformers, DDB Series, Models DDB-72..170.

› Capacitive Voltage Transformers, DFK Series, Models DFK-245..765.

› Coupling Capacitors, DDN Series, Models DDN-72..170.

› Coupling Capacitors, DFN Series, Models DFN-245..vvz765.

DESIGN/

Capacitive voltage transformers consist of 1 or more capacitor units mounted on a tank containing the electromagnetic unit (intermediate transformer, compensation reactance and auxiliary elements).The tank is fi tted with a box containing the secondary terminals and the adjustment compensations (they are protected by a sealed cover).

Oil volume variations in the capacitor unit(s) are compensated for in one or more metal diaphragms located at the top of each unit. In the inductive part (tank), the oil level is displayed by a direct indicator. Each insulator is hermetically sealed and independent.The coupling capacitors have the same characteristics as previously indicated for capacitive voltage transformers but without the electromagnetic unit (EMU).

1. Primary terminal2. Oil volume compensating system3. Insulator4. Capacitors5. Intermediate voltage tap6. Inductive voltage transformer7. Secondary terminal box

8. Upper Capacitor Unit9. Intermediate Capacitor Unit10. Lower Capacitor unit11. Electromagnetic Unit (EMU)12. Carrier accessories (on demand)

1

3

5

6

7

2

2

3

4

4

8

10

9

11

12


User manual

TRANSPORT/

TRANSPORT AND HANDLING

ARTECHE’s packaging guarantees a correct transport to destination.

Transport must always be carried out in a vertical position, in wooden boxes.

If the transformer is made up of several capacitor units, it is shipped disassembled, with all the capacitor units inside the same box, each one anchored to the base of the packaging, except the lower one, which is attached to the tank.

For transport, the transformer should be properly attached to the packaging so as to avoid movement.

› Load and unload the transformer slowly and avoid sudden movements.

› It must be secured to the truck to avoid movement.

› Keep truck acceleration under 5G, and the speed under:

• Unpaved road ___________ Max. 30 km/hour

• Secondary roads ___________ Max. 60 km/hour

• Highway (Motorway) ___________ Max. 90 km/hour

STORAGE/

The storage area must maintain the necessary health and safety conditions so as to avoid damage to the transformer. Follow the safety markings on the packaging at all times.

› Always store in an upright position: The transformers must be stored upright in their original packaging, which was designed to this end.

Wooden packaging loses its properties over time, especially when exposed to the elements.

Therefore, transformers cannot be stored in their packaging indefi nitely. This period depends on the type of wood, temperature, humidity, contamination, etc. It is recommended to check the integrity of the packaging regularly.

After unpacking the transformers, if they are not to be installed immediately, always store them fi rmly anchored to the ground without time restriction.

The fi nal holder will be responsible for delivering the used packaging or its waste for environmental management according to the legislation in force in their country.

HANDLING/

It is recommended to transport the packaged transformers to the construction site.

Unpacking: Remove the top and sides of the box to allow free handling of the unit.

Annex I, contains the fi gures mentioned below.

The movements are to be carried out as shown in fi g. 1.

For transformers consisting of a single capacitor unit, the slings must be placed in the holes prepared for this purpose in the base and, before lifting, the screws that join the unit to the base of the packaging must be loosened.

DANGERINJURIES from falls and tipping

› Do not place the equipment upside down or on its side

› Do not transport the equipment in conditions other than those mentioned

RECEIPT/

After receipt, check the packages for signs of shock, tampering, etc. Any anomaly must be indicated on the transport company’s receipt sheet and communicated to ARTECHE or the equipment supplier.

Once the transformer has been unpacked, check that none of the screws holding the insulator have become loose during transport. If they have, tighten them according to the torque indicated in Annex II. If any other type of anomaly appears, inform ARTECHE or the supplier of the equipment.

Attach pictures of the damaged transformers with the report.

› Possible damage to the packaging: Dents on the outside, open packaging, etc.

› Possible damage to equipment: Broken or defective insulator, dented metal parts, damaged secondary terminal box, etc.

The packed units can be moved by forklift or with slings and/or chains. Follow the safety markings on the packaging.

DANGERINJURIES AND/OR FIRE

› Do not use damaged equipment

DANGER

INJURIES from falls and tipping

› Do not place the equipment upside down or on its side

› Handle the transformer according to the instructions in this manual

› A sling which is in good condition and is suitable for handling the equipment should be used according to the equipment’s weight, indicated on the nameplate

Under no circumstances should a transformer be manipulated by pulling on the primary terminalsThis may cause damage to the equipment and void its warranty

For multiple capacitor units, never move the entire unit suspended by its head. Always move it from the base (tank) fi g. 1a, fi g. 1b


User manual

INSTALLATION

MOUNTING ON THE STRUCTURE OR PLATFORM/Check the information on the nameplate to verify that the electrical characteristics match those of the system.

Carefully check that all four legs of the transformer are perfectly placed on the platform before tightening the anchor bolts.

If this is not the case, correct the defect, by wedging metal plates or similar. Failure to do so may result in insulator breakage or oil leakage.

The slings must be attached to the upper fl ange area of the insulator to prevent it from tipping over during the operation (see fi g. 1b).

DANGER

INJURY AND/OR FIRE

› Do not install the equipment without following our specifi cations

› Use the transformers under proper service conditions and according to specifi cations

› Do not loosen any screws or fastening nuts, it can cause oil leaks

ELECTRICAL DISCHARGE

› Do not wire or connect when the equipment is in operation

› The ground terminal of the apparatus must be solidly earthed by means of a connection capable of withstanding and conducting the line’s fault current to earth.

› Do not short-circuit the secondary circuit of the transformer

Indications for units consisting of several capacitor units:

› For the lower unit, proceed as described above.

› For all other capacitor units, the slings are to be tied to the upper fl ange of the isolator (see fi g. 1c) or to the eyebolts of the cover (see fi g. 1d).

Only the fastening screws in the packaging must be loosened as shown in fi g. 2, otherwise the tightness will be broken and oil will leak out

Once the equipment has been unpacked, a visual inspection is suggested so as to detect possible oil leaks or stains.

Oil stains are not necessarily the result of a leak. In most cases, the stains are nothing more than oil residues from the

manufacturing process.

The stain should be cleaned with a degreaser and the equipment should be kept under observation. If the stain reappears or spreads, contact the manufacturer.

TRANSFORMER MOUNTING (when the unit consists of several capacitor units)/The assembly of the transformer made up of several capacitor units must be carried out on the structure in the following sequence:

1. Lower capacitor unit: › Remove the protective cover of the compensators from the upper part (fi g. 3), keeping the nuts for subsequent attachment of the upper unit.

› Lift it onto the structure as described in the handling section and fi g. 1b.

2. Intermediate capacitor unit (if any): › Remove the protective cover of the compensators from the upper part (fi g. 3), keeping the nuts for subsequent attachment of the upper unit.

› Only the screws that connect the unit to the base of the packaging should be loosened. The unit is now ready to be lifted (fi g. 2).

› To lift it as described in the chapter on handling and fi g. 1c and fi g. 1d.

› This unit is placed on top of the lower unit by connecting the cable between the two to the threaded hole at the bottom of the upper unit by means of the screw provided (fi g. 4.) Both units are to be coupled with the stud bolts that have become free after removing the protection disc (fi g. 5.) The tightening torques are given in Annex II.

3. Upper capacitor unit: Proceed as in point 2 (Not applicable the point regarding the protective cover).

Do not forget to make the electrical connections between the capacitor units Check that the serial numbers on the same transformer match

If an already installed unit is disassembled, proceed in the opposite way to that indicated, not forgetting to fi t the short-circuit cable to all the capacitor units.

Keep the grounding switch of the carrier accessories (if applicable) in the closed position.


User manual

ELECTRICAL CONNECTIONS/Primary connections

The primary terminal material is aluminum or copper. They can have a tin or silver coating to prevent galvanic pair corrosion and improve their contact.

Do not bring aluminum into contact with copper-based materials unless special precautions are taken.

Material Finish Cleaning

CopperSilver or tin plated We recommend cleaning the contact surfaces with

a soft cloth (avoid brushing with a metal brush)Aluminum

Aluminum Unfi nished

We recommended vigorously brushing the contact surfaces with a soft metal brush (preferably

stainless steel) or sandpaper, until you see the characteristic shine of the clean metalCopper/Brass

Only impregnate the contact surfaces to be used with contact grease, keeping the others clean. Remove excess grease to avoid contamination.

Tightening must be carried out using a torque wrench, as shown on the diagram plates and in Annex II.

Check the correct external wiring.

Grounding

The ground terminal of the transformer must be properly connected to the ground network by a connection capable of carrying the network’s fault current. Check that the connection is tightened correctly and that the contact surfaces are clean.

The low voltage terminal of the primary voltage winding must always be grounded when the transformer is in service. This terminal can be located inside the secondary terminal box on the side of the box (fi g. 7).

The high-frequency terminal (HF), which protrudes from the capacitor unit, must be fi rmly connected to the ground terminal of the housing (fi g. 8a). If there are carrier accessories, this high frequency (HF) terminal shall be connected to the carrier accessory block. While this equipment is not in use, the grounding switch must remain closed (fi g. 8b).

A faulty contact or a bad connection can lead to rapid transformer deterioration

Avoid excessive torque, as the connector may suff er damage such as cracks which may expand in the future and cause it to break

An inadequate torque may cause improper contact and cause the terminals to heat up during operation

Secondary connections

The secondary winding(s) must be connected to earth through one of its terminals, preferably in the secondary terminal box itself.

In case of secondary with intermediate taps, the common termi-nal must be grounded.

Check that the secondary connections are correctly tightened and the contact surfaces are clean.

The screws of the lower cable gland cover, the block cover and the terminals must be tightened to the torque specifi ed in Annex II.Do not leave the terminal block open after handling. It should be properly closed with the cover and lid.

In the terminal box there is a block where the secondary wires are connected. The disposition of the terminals is indicated on

the secondary marking plate on the inside of the box cover.

Any secondary one that is not loaded must be open and grounded at a single point

The current in a short-circuited secondary can reach dangerous values and can even destroy the device

CAUTION

Do not use the secondary terminal block as a stepA platform lift or ladder should be used to make or check the primary connections, upholding the necessary safety conditions for work at height. Under no circumstances may the terminal block be used as a support


User manual

Always follow the Arteche Manual for instructions on transport, storage, handling and installation.ARTECHE instrument transformers do not require maintenance. There are no moving parts and no components susceptible to wear and tear, so no active maintenance is required.

However, some companies perform some maintenance operations on instrument transformers as part of a general substation maintenance program. These maintenance programs are not intended to extend the life of the units, as the measures have no impact on the state of the insulation or the performance of the units. These programs serve to know the state of the isolation, so that the user can make decisions based on the results obtained, as well as detect situations that may be causing damage to the unit.

We at Arteche, as manufacturers, do not establish any specifi c measures, since the decision depends on:

› the resources available to each user,› the location of the instrument transformer (can be a position

which is more or less critical),› the environmental and electrical conditions that the unit must

withstand at each specifi c point,

› the history of the unit,› the specifi c types or the problematic units,› etc…

The following inspection points are only a suggestion in case they are within the user’s maintenance policy.

1. Physical inspection:a. a. Mechanical: Look for signs of impact, damage or loose

parts.b. Electrical: Check the correct state of the electrical

connections.c. Oil: Look for oil leaks and check the oil level.

2. Dielectric tests:d. Electrical tests to evaluate the insulation of the equipment.

For the test procedure, see Annex III.3. Thermographic testing:

e. Use of thermographic cameras.

ARTECHE off ers a diagnostic service for capacitive voltage transformers in the fi eld. More information: www.arteche.com.

INSPECTION AND MONITORING

DANGER

ELECTRIC SHOCK AND/OR INJURY

› Everything should only be carried out by personnel who is qualifi ed in the maintenance and verifi cation of the equipment

› Do not touch live parts

Final Considerations

DANGER The transformer must be fi rmly grounded. A faulty or missing connection may cause damage or even destroy the device

Once the installation has been completed, the short-circuit cable must be removed from each capacitor unit before energizing the transformer (see fi g. 9.) This cable is used to prevent the capacitor from being charged during storage and handling

If the transformer is equipped with a grounding switch for the electromagnetic unit, it should only be used for maintenance purposes. It is not intended for permanent earthing of the electromagnetic unit in operation, as the insulation of the capacitor part would be reduced (fi g. 10)

Resin block:› Transformer adjustment taps and ferroresonance protection

circuit connection links, covered by a protective cap which is sealed at the factory. Do not open the box.

› The main protection circuit is located on the protection cover, connected to the terminals “RS1” and “RS2” marked on the block itself. Important: This main protection circuit must be always connected.

[1] [2]

[3] [1]

[3]

1. Protective cover for adjustment taps.2. Main ferroresonance protection circuit (only accessible for the resin block).3. Precinct.

Metal block:› Transformer adjustment taps and ferroresonance protection

circuit connections, covered by a protective cap which is sealed at the factory. Do not open the box.

The following elements are located on the right side of the terminal block:


User manual

Type Code Test Observations

Phy

sica

l ins

pec

tio

n

A1 Packaging Look for signs of rough handling.

A2 Insulator Check that is not damaged and is clean. Check that it is not loose, bent or broken.

A3 Primary Terminals Check that they are not loose, bent or broken.

A4 SecondaryTerminal

Box

Check that it is not damaged and that it is securely fastened to the tank or transformer holder.

Check that no water enters the terminal box due to rain.Check that the ventilation openings are not blocked.A5

A6 Metal parts Check for dents, scratches or signs of corrosion.

A7 Unusualbehavior Check for unusual noises, vibrations or odors.

B1 Primary connections

Check that there is good contact, that there are no signs of corrosion and that all nuts and bolts are properly tightened. The use of conductive grease such as Penetrox A13 is recommended to improve contact.

B3 Secondary circuits

Check that all screws are properly tightened, and that there are no signs of corrosion.In the case of secondary windings with intermediate taps, check that the connection matches the real transformer ratio. Check that the unused secondary windings are in open circuit.

B4 Grounding Check that the grounding terminal is correctly connected to the substation grounding network, that the screws are correctly tightened and that there are no signs of corrosion.

B6

Voltage transformer

neutral connection

Check that the neutral terminal (N) of the primary winding is grounded. Leaving it open when the transformer is energized will cause surges and damage to the

transformer.

B7 Readings Check that the reading values of the secondary match the values expected.

B8 AF connection Verify that the high frequency (HF) terminal is connected to ground or to the accessory block. While this equipment is not in use, the carrier wave groundings witch must remain closed.

C1 Oil level indicator Check the oil level in the tank through the sight glass.

C2 Oil stains or leaks

Check the following areas for visible oil traces: › Insulator fl anges › Junctures between parts of the metal enclosure › Junctures between the secondary terminal box and the tank or base › Primary terminals’ surrounding area

Die

lect

ric

test

s

D1 PF/DDF/tgδ

The limit values of this parameter depend on the transformer’s voltage level. The recommended values are given with the order. It is also important to control this parameter’s change over time. A change in the value of this parameter indicates a change in the properties of insulation, but it is not defi nitive proof of faulty insulation. For this reason, if the value of the delta tangent is above the recommended value or has increased, a careful investigation should be carried out and further testing may be required. In this case, contact Arteche for assistance.For details on the test procedure, follow Annex III.

D2

Measurement of the

Insulation resistance

For fi eld tests, the use of the megohmmeter (Megger) is very common, and the tests that are usually done are: › N/P2 against secondary and Ground › Each secondary against ground › Among the secondaries

In the case of new equipment, the value obtained does not provide any information, unless a short circuit is detected. Generally, values above 200 MΩ should be expected. However, the comparison of long-term values - such as in the case of tanδ, or of power factor - can help determine if a device is still in good working conditions. Do not test at voltages above 3 kV AC or 1 kV DC. Do not test for more than one minute. It is not recommended to repeat this test often as the

internal insulation could be damaged. For details on the test procedure, follow Annex III.

D3 Ratio test

The Portable Transformer Ratio Meter is commonly used to measure the ratio, excitation current and polarity of windings. The values obtained are a reference that the transformer is in good condition and can be energized. They should not be compared with the results of factory tests carried out in the manufacturing plant laboratory.Due to the high precision required for this measurement, the actual uncertainty of the test must be taken into account when testing on site.For details on the test procedure, follow Annex III.

Ther

mo

gra

phi

c te

sts

E1 Thermographic analysis

Using thermographic cameras, hot spots can be detected during the operation of transformers. In most cases, hot spots on instrument transformers occur at the primary terminals’ connection point to the line. If present, check the integrity of the connectors, as well as their correct position and whether they are correctly tightened.


User manual

TESTS PROGRAM/

CAREFUL CHECK OF THE TRANSFORMER/It is recommended that all regular tests be repeated after a long period of operation (about 20 years), or if a major network disturbance has occurred that could damage the transformer

(e.g. a short circuit with current or duration values higher than the nominal ones, or over-voltages caused by the malfunctioning of the switches).

QUICK TROUBLESHOOTING GUIDE

Phenomenon Cause Countermeasure

Oil stains

Oil residues from the manufacturing process

Clean the area and keep it under observation for 24 hours. If the stain does not reappear,

the device can function normally. If the leak persists, contact ARTECHE

Loose juncturesTighten the screws and bolts, clean the

area and keep it under observation.If the leak persists, contact ARTECHE

Cracks or damage to components Contact ARTECHE

Non-visible oil level Oil leakage or overpressure Remove the transformer from service and contact ARTECHE

Cracks in resin parts Blows or improper handling Contact ARTECHE

When WhatOn arrival of the transformers at the warehouse or substation A1

After unpacking A2 - A3 - A4 - A6 - C2

During assembly A2 - A3 - A4 – A5 - A6 - B1 - B3 - B4 - B6 - B8 - C1 - C2 - D2 - D3

After energizing A7 - B7 - C1 - C2 - F1

Routine checks (weekly or monthly) A2 - A7 - B7 - C1 - C2

Annual verifi cations A2 - A3 - A4 - A5 - A6 - A7 - B1 - B3 - B4 - B6 - B7 - B8 - C1 - C2 - F1

Every fi ve yea Same as annual + D1

After re-connections, load changes A7 - B1 - B3 - B4 - B6 - B7 - B8 - F1

After the fault conditions, the short circuits, etc. A3 - A7 - B1 - B3 - B4 - B6 - B7 - B8 - C1 - C2 - D1See also “Careful check of the transformer” below

User manual - Annex I High Voltage Instrument Transformers | DDB/DFK/DDN/DFN

ANNEX I

› DDB-72..170

HANDLING AND CONNECTION

› DFN-245..765› DFK-245..765 › DDN-72..170

1

User manual - Annex I

High Voltage Instrument Transformers | DDB/DFK/DDN/DFN

1a 1b 1c 1d

› Fig. 2: Loosen only these screws

› Fig. 1: Handling

FIXING SCREW

4 FIXING SCREWS

DO NOT TOUCH - OILTIGHTNESS DO NOT TOUCH - OILTIGHTNESS

THE UNIT IS FIXEDBY MEANS OF THE4 FIXING SCREWS

4 NUTS ARE USED TO FIX IT TO THE PACKAGING.REMOVE THEM FOR

UNPACKING

2



› Fig. 3: Protective cover

› Fig. 5: Assembly between capacitor units

› Fig. 4: Connection cable for capacitor units

3



› Fig. 6: Level indicator › Fig. 7: Neutral grounding connection

› Fig. 9: Short-circuit cable of capacitor unit Remove only before energizing › Fig. 10: Grounding switch

› Fig. 8b: HF connection with carrier accessories› Fig. 8a: HF grounding without carrier accessories

User manual - Annex II High Voltage Instrument Transformers | DDB/DFK/DDN/DFN

ANNEX II

SCREWTYPE

TORQUE WRENCH SETTING (Nm)

USE TORQUE WRENCH SETTING

M12/16/20 Fixing the insulator to the base 30 Nm

M12 Support between capacitor units 30 Nm

M12 Insulator fl ange to intermediate plate 30 Nm

M6 Connection cable between capacitor units 12 Nm

M8 Tank Lid 30 Nm

M8 Primary Terminals 20 Nm

M8 Secondary terminals (if they are of the screw type) 12 Nm

M6 Grounding (inside secondary terminal box) 12 Nm

M10 HF terminal 12 Nm

M6 Cable gland 12 Nm

M8 Terminal Block Cover 20 Nm

M6 Bottom closing lid of the terminal block 12 Nm

TIGHTENING TORQUES

NOTE: If a torque diff erent from that indicated in this table is indicated on the drawing or plates of the equipment, the torque indicated on the drawing or plate must be applied.

User manual - Annex III High Voltage Instrument Transformers | DDB/DFK/DDN/DFN

ANNEX III

ELECTRICAL FIELD TESTING

All ARTECHE transformers are assessed at our High Voltage laboratories, under the strictest criteria of international standards and/or under specifi c client standards/specifi cations when so requested. All of it under a thorough quality system, certifi ed under ISO 9001. However, it is normal for pre-operative tests to be performed in order to confi rm certain important equipment values. The following is a guide to the most common on-site tests and the proper way to perform them on ARTECHE brand transformers.

This annex applies to the following equipment:

› Capacitive Voltage Transformers, DDB Series, Models DDB-72..170.

› Capacitive Voltage Transformers, DFK Series, Models DFK-245..765.

› Coupling Capacitors, DDN Series, Models DDN-72..170.

› Coupling Capacitors, DFN Series, Models DFN-245..765.

6

User manual - Annex III


MEASUREMENT OF CAPACITANCE AND DIELECTRIC DISSIPATION FACTOR (tanδ)

The purpose of this test is to assess the insulation of the HV transformer.

NOTE: Field testing of tanδ may be susceptible to diff erences in measured values from factory testing due to the following factors:

› The type of test equipment used and the measurement voltage level.

› Thermal conditions (high humidity, rain, pollution).

› Temperature of the test object.

› Stress induced to the test object through other equipment.

It is recommended that the surfaces of the transformer (insulators and others) be clean, to avoid external leakage currents.

Test instruments for fi eld use are usually equipped with solutions to compensate for external leakage current. The voltage test for this particular equipment is typically 10 kV for high voltage insulation and approximately 2.5 kV for low voltage insulation.

Tanδ and capacitance measurement can also be performed in the fi eld using other low voltage test bridges and a transportable high voltage test set capable of measuring voltages up to the nominal voltage. The choice and application of various test equipment is at the discretion and experience of the user.

In addition to the measurement of tanδ, the measuring equipment can usually also measure other parameters such as capacitance and power factor.

The delta tangent measurement is carried out with the same layout as the capacitance measurement.

Measurements can be made of tanδ and capacitance of the capacitor unit(s), Cn, C1 and C2.

All measurements must be made with the equipment switched off and with a test voltage <10 kV for measurements Cn and C1 and <2 kV for measurement C2.

Cn - Total rated capacitanceThe rated capacitance Cn of the unit is the capacitance value between the high voltage terminal (number 1 in fi g. 1) and the low voltage terminal (number 3 in fi g. 1.)

The capacitor voltage divider is designed to meet the rated capacitance Cn.

This value, with some tolerance allowed, is engraved on the nameplate.

The value of Cn is calculated with the following formula: Cn=( 1∗ 2)/( 1+ 2)Test procedure (fi g. 2):

› Disconnect the HF connection to ground.

› The (HV) power cable of the measuring equipment must be connected to the primary terminal (A/H1).

› The measurement cable must be connected to the high frequency terminal (HF).

C1 - High voltage capacitanceThe high voltage capacitance C1 corresponds to the part of the capacitor connected between the line terminal (number 1 in the fi g. 1) and the intermediate voltage terminal of the capacitive divider (number 2 in fi g. 1).

This test can only be performed in the fi eld if the transformer has a grounding switch, since point 2 is not directly accessible because it is inside the lower capacitor unit. For that reason, the

way to measure this capacitance is to close the grounding switch, thus short-circuiting the electromagnetic unit and connecting point 2 in the fi gure to ground. The measurement will be made directly between the high voltage terminal (number 1 in fi g. 1) and the transformer tank or transformer ground.

Test procedure (fi g. 3):


› Close the grounding switch.

› The (HV) power cable of the measuring equipment must be connected to the primary terminal (A/H1).

› The measuring cable must be connected to the ground terminal of the transformer.

C2 - Capacitance of the intermediate voltage capacitorThe capacitance of the C2 intermediate voltage capacitor corresponds to the part of the capacitor connected between the intermediate voltage terminal of the capacitive divider (number 2 in fi g. 1) and the low voltage terminal (number 3 in fi g. 1).

This test can only be performed in the fi eld if the transformer has a grounding switch, since point 2 is not directly accessible because it is inside the lower capacitor unit. For this reason, the way to measure this capacitance is to close the grounding switch, thus short-circuiting the electromagnetic unit and connecting point 2 in the fi gure to ground. The measurement will be made directly between the low voltage terminal (number 3 in fi g. 1) and the transformer tank or transformer ground.

Test procedure (fi g. 4):


› Close the earthing switch.

› The power supply cable (HV) of the measuring instrument must be connected to the high frequency (HF) terminal (low voltage terminal).

› The measuring cable must be connected to the ground terminal of the transformer.

CAPACITIVE VOLTAGE TRANSFORMERS AND COUPLING CAPACITORS/

7



Capacitance of each capacitor unitThe capacitance of each capacitor unit can be measured directly between the fl anges of the insulators, with the exception of the bottom insulator.

Test procedure for intermediate capacitor units or higher:

› The power supply cable (HV) of the measuring equipment must be connected to the higher fl ange or the primary terminal.

› The measuring cable must be connected to the lower fl ange of the capacitor unit.

Test procedure for the lower capacitor unit:


› The (HV) power cable of the measuring equipment must be connected to the primary terminal (A/H1) or the higher fl ange.

› The measurement cable must be connected to the high frequency terminal (HF).

1

3

TERMINAL A/H110 kV

Cn / FP GST-GND

AF / HF

TERMINAL A/H110 kV

C1 / FP GST-GND

TANQUE

2 kVAF / HF

TANQUE

C2 / FP GST-GND

› Fig. 1a › Fig. 1b

› Fig. 2 › Fig. 4 › Fig. 3

High Voltage Terminal

High Voltage Capacitance

Intermediate Capacitance

Electromagnetic unit

Carrier accessories(if included

with unit)

GroundingSwitch(if includedwith unit)

C1

1

C2

2

3

8



The measurement of the insulation resistance is done to check the integrity of the transformer insulation and to ensure that it has not been internally damaged during transportation.

This test depends largely on the design of the transformer, the general confi guration of the test, the instruments used, etc.

The values obtained may not be representative of the actual state of the insulation.

If this test is performed, it is recommended to contact the manufacturer.

For fi eld tests, the use of the megohmmeter (Megger) is very common, and the tests that are usually done are:

› Neutral against secondary and ground.

› Each secondary against ground.

› Among the secondaries.

In the case of new equipment, the value obtained does not provide any information, unless a short circuit is detected. Generally, values above 200 MΩ should be expected. However, the comparison of long-term values - such as in the case of tanδ, or of power factor - can help determine if a device is still in good working conditions.

Do not test at voltages above 3 kV AC or 1 kV DC.Do not test for more than one minute. It is not recommended to repeat this test often as the internal insulation could be damaged.

INSULATION RESISTANCE MEASUREMENT

CAPACITIVE VOLTAGE TRANSFORMERS/

Neutral against Secondaries + Ground N/S+G › The line cable of the measuring equipment must be connected to the terminal N/H2* disconnecting the grounding link of the primary winding.

› The ground cable of the measuring instrument must be connected to the short-circuited secondary terminals together with the ground terminals on the secondary terminal block as well as the tank.

Secondaries against Ground S/G › Primary terminal A/H1 must be disconnected and the neutral connection of the (N/H2*) primary winding must be grounded.

› The line cable of the measuring equipment must be connected to the short-circuited secondary terminals.

› The grounding cable of the measuring equipment must be connected to the tank.

Between secondaries S/S › This test is only applicable to transformers having more than 1 secondary.

› Primary terminal A/H1 must be disconnected and the neutral connection of the (N/H2*) primary winding must be grounded.

› The secondaries to be assessed will be connected; one to the line cable and the other(s) to the ground cable of the measuring equipment.

› The test is repeated with each secondary.

* The N or H2 terminal can be located inside the secondary terminal box on the side of the box.

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The Portable Transformer Ratio Meter (TTR) is commonly used to measure the ratio, excitation current and polarity of windings.

The values obtained are a reference that the transformer is in good condition and can be energized. They should not be compared with the results of factory tests carried out in the manufacturing plant laboratory.

Due to the high precision required for this measurement, the actual uncertainty of the test must be taken into account when testing on site.

The TTR contains 4 terminals (this confi guration may vary depending on the manufacturer):

› H1: Black excitation terminal.

› H2: Red excitation terminal.

› X1: Black secondary terminal.

› X2: Red secondary terminal.

TRANSFORMER RATIO TEST

This test verifi es the transformer ratio and polarity, and displays a “+” signal if correct, and a “-” signal if inverted. To carry out the test, proceed as follows (fi g. 5.

› The excitation terminals (clamps marked “H”) will be connected to the transformer’s primary circuit:

• H1 will be connected to the primary terminal of equipment A/H1.

• H2 will be connected to the ground terminal, located at the base of the equipment.

› The clamps marked “X” will be connected to the transformer’s secondary terminals:

• X1 will be connected to the beginning of the winding. When the secondary has taps, you must connect X1 to the tap of the secondary terminal which is to be tested.

• X2 will be connected at the end of the secondary winding.

• This test must be applied to each secondary separately; in case the transformer has more than one secondary, the secondaries which are not to be tested must be left open.

CAPACITIVE VOLTAGE TRANSFORMERS/

A/H1

H1

H2

X2X1

a1 a2 a3

T.T.R.n

› Fig. 5

User manual

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MU_HV_DDB_DFK_DDN_DFN_ENV: A0 09/04/2021

HIGH VOLTAGE INSTRUMENT TRANSFORMERS DDB/DFK DDN/DFN

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