TS3_LT8_HIGHVOLT_On-site testing of transformers

HIGHVOLT Prüftechnik Dresden GmbH

Dr. Mario Jochim

SAVE COSTS AND TIME ASSURE QUALITY

On-site testing of transformers

Dr. Mario Jochim, HIGHVOLT PRÜFTECHNIK Dresden GmbH 222

Agenda

§ Motivation

1

1.1

1.2

§ Areas of Application 2

2.1

2.2

2.3

§ Modules of the High Voltage test system

3

§  Induced voltage test

3.1

§ Applied voltage test

3.2

§ Summary

4

Motivation

Ø Mobile test systems are an essential part of quality assurance during manufacturing, repair and diagnostics on-site


§  Saving time and costs by repairing of transformers on-site

§  Essential assembly for large power transformers takes place on-site (Logistical limitations)

§  Diagnostics are being improved

§  Flexible test system use on-site and in the factory

Area of application: On-site repair of transformers

Ø Mobile on-site test systems are necessary to guarantee quality assurance equal to factory testing


§  Transport of faulty transformer to factory is costly and risky

§  Infrastructure limitations (narrow roads, live load of bridges, etc.) do not allow transportation of transformer

§  Prolonged down time/repair time of transformer due to return transportation

§  On-site repair is an attractive alternative (both cost and time-wise) to factory repair

Area of application : Essential assembly for large power transformers on-site §  Infrastructure limitations (narrow roads, live load of bridges, etc.) do not allow

transportation of transformer in whole

§  Large transformers are shipped in parts

§  Final assembly has to be performed on-site


Ø Mobile on-site test systems are necessary to guarantee quality assurance equal to factory testing

Area of application : Diagnostics are being improved by HV tests §  Improved determination and elimination of interferences due to change of

test frequency

§  Improved failure recognition due to evaluation of partial discharge (PD) inception and extinction voltage by change of the test voltage

§  On-site test results comparable to factory tests

Ø Mobile on-site test systems improve diagnostic value


Area of application : Flexible test system use: on-site and in the factory §  Some repair will be performed on-site and some in the factory

§  Mobile test systems increase redundancy, capability and quality comparability and therefore ensure better performance

§  Test results on-site and in the factory needs to be according to the relevant standards

§  Back-up for maintenance, repair and outage of MG-sets

Ø Mobile test systems can be used flexibly on-site and in the factory and save investment cost


Modules of mobile test systems require:

§  Fulfillment of corresponding standards like IEC 60076-3, IEEE C57, GOST 1516.3

§  Compact design for easy transportation worldwide

§  Fast installation and testing

§  Multiple use for fast return on investment

à In short: mobile test systems have comparable functions to stationary test systems but are more compact, robust, assembly friendly, quality focused and multi functional

Ø On-site test results needs to be comparable to results from the factory, R & D


9 Dr. Mario Jochim, HIGHVOLT PRÜFTECHNIK Dresden GmbH

Induced voltage test system on a 40 ft trailer Power: 620 kW, 1.000 kVA for power transformers up to 500 MVA

Space for accessories

Static frequency converter

Step-up transformer

Control room HV filter 1

Power supply cable, HV connection cable

CT’s and VT’s

Space for accessories, HV electrodes, etc.

HV test lead

Ø Compact on-site transformer test system Ø Ready to operate within 1 hour

§  Compact and on-site proven design on: 1 x 40 ft trailer 3 x 20 ft containers

§  Units world wide in service


Induced voltage test system in 3 x 20ft containers Power: 620 kW, 1.000 kVA for power transformers up to 500 MVA

Table: Parameters of the test system

Ø The test system provides results directly comparable to factory test, conformity to corresponding standards

Test System Type WV 620-1200/80

Active power 620 kW

Apparent power 1,000 kVA

Max. output voltage 80 kV

PD level < 50 pC

THD < 5 %

Frequency range 40…200 Hz


TRANSFORMERS TO BE TESTED UP TO APPROX.

Capability of test system for induced voltage test

Test WV 620-1000/80

No-load losses test

350 MVA (500 MVA with THD > 5 %)

Load losses/ short-circuit test 30 MVA

Induced voltage test 500 MVA

Applied voltage tests 46 kV

Ø Essential induced voltage tests can be performed on a large scale on power transformers

Mobile compensation unit (HVCC 24000/36) §  Current transformer for high accuracy load

loss measurement §  Advanced protection system §  Motorized cable drums for easy set-up

(preparation time approx. 1 hour)


Mobile extension for load losses test – HVCC 24000/36

Table: Parameter of HVCC 24000/36

Output terminals

Motorized cable drums

Ø Mobile capacitor bank allows to perform short circuit, load loss and temperature rise test

Extension for load loss testApparent power 24,000 kVAMay. Output voltage 36 kV


THREE POSSIBILITIES OF EXTENSION

How to test bigger transformers?

1 Transformer test system WV 2 HV Capacitor bank HVCC 3 HV Compensation reactor 4 HV Transformer for applied voltage test 5 Transformer to be tested 2nd Transformer test system

Capacitor bank HVCC

Reactor

Ø Even for very large power transformers on-site tests can be arranged

§  Parallel connection of up to 3 units possible

§  Suitable for high active power requirements of the test object

§  Available test power of 1.9 MW/3 MVA (3 systems in parallel)


2nd MOBILE TRANSFORMER TEST SYSTEM

Extension for no-load losses test

Test WV 620-1000/80 with Extension (2nd system in parallel)

No-load losses test 350 MVA (500 MVA with THD > 5 %)

700 MVA (1.000 MVA with THD > 5 %)

Table: Transformers to be tested


TRANSFORMERS TO BE TESTED (UP TO APPROX.)

Mobile extension for load losses test – HVCC 24000/36

Test WV 620-1000/80 with Extension (mobile HVCC 24000/36)

Load losses/short-circuit test 30 MVA 150 MVA

+

Ø Mobile capacitor bank allows to perform short circuit, load loss and temperature rise test



Inductive compensation

Test WV 620-1000/80 with Extension (inductive compensation)

Induced voltage test 500 MVA 1000 MVA

+ Compensation reactor


Applied voltage test system

RESONANT SYSTEM WITH VARIABLE FREQUENCY

Wide load range of power transformers 1.3 to 21.5 nF §  Variable test frequency 40 to 200 Hz §  Test voltage up to 720 kV §  Set-up time approx. 1 hour

Ø Test system can also be used for test of GIS and short cables



Conclusion

Test WV 620-1000/80 With Extension / second test system

No-load losses test 350 MVA (500 MVA with THD > 5 %)

700 MVA (1.000 MVA with THD > 5 %) (2nd system in parallel)

Load losses/ short-circuit test 30 MVA

150 MVA (mobile HVCC 24000/36)

Induced voltage test 500 MVA 1000 MVA (compensation reactor)

Applied voltage tests 46 kV 300 kV (applied voltage extension) 720kV (WRV system)

Ø Modular structure test system allows cost effective testing even of large power transformers

Summary

§  On-site high voltage tests on transformers are getting more important in the future due to on-site repair, diagnostics, installations and quality conformation

§  Test systems can be used for transformers but for GIS and cables too

§  Due to conformity with standards HV test systems can be used in the factory too

§  Double use in factory and on-site helps to save investment costs


HIGHVOLT Prüftechnik Dresden GmbH HIGHVOLT Prüftechnik Dresden GmbH

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TS3_LT8_HIGHVOLT_On-site testing of transformers