14_bergmann_hv tr.pdf
TRANSCRIPT
HIGH VOLTAGE TESTING ON TRANSFORMERS
CEPED 2013, Bali, Indonesia
Dr. Ralf Bergmann
HIGHVOLT Prüftechnik Dresden GmbH
Table of contents
Motivation and Standards
Factory Testing – Latest Technology
On-Site Testing – Same principle
Summary
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MOTIVATION AND STANDARDS
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Motivation
Early recognition of:
Design issues
Production failures
Insulation degradation
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Motivation
Transformer - Key component in electric energy system
Securing Transformers‘ quality essential for reliability of electric network
Extensive testing within development and testing of transformers Routine test Type test
Increase of old transformers in power grid Need to verify old transformers‘ condition
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STANDARDS FOR FACTORY TESTING
Standards
Standards IEC IEC 60076-1…3
Standards IEEE IEEE C57.12.00 - C57.12.90 IEEE C57.152 (= old IEEE 62)
GOST GOST 1526, GOST 3484, GOST 52719-2007
On-Site Testing: No separate standards. use of same testing procedures, possible test voltage reduction for service aged
transformers
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Possible Test`s on power transformers
Measurements of winding resistance Measurement of no-load loss and current
Dielectric tests Temperature-rise test
Determination of sound levels
Measurement of the harmonics of the no-load current
Measurement of insulation resistance
Measurement of turn ratio
Determination of capacitances Tests on on-load tap-changers
FACTORY TESTING - LATEST TECHNOLOGY
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IMPULSE VOLTAGE TEST OF POWER TRANSFORMER ACCORDING TO IEC 60076-3, POS. 13-15 IEC 60060-1 2010
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Sample of lightning impulses
Tail time
Front time
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0,9
0,3
1,0
U
B
A
0,7a
t T1
TC
a
D
C
0,1a
a – instant of chopping
Full lightning impulse Chopped lightning impulse
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Accuracy is important:
Correctness of wave shape
Space is expensive:
Space saving solution
Time is money:
Quick test setup increasing output of factory
Requirements on impulse voltage test
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Connection Point – The all in one solution
Test system consists of only two individual components: 1) Impulse generator 2) Connection Point HV divider Chopping gap and Overshoot compensation
Benefits of Connection Point: Space saving solution Integrated overshoot compensation Only one connection to the test object Only one test setup is used
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Space reduction using Connection Point
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Arrangement with Connection Point Arrangement with divider, overshoot compensation and chopping gap
MOST COMMON LAYOUT LAYOUT USING CONNECTION POINT
Example: Test system ULI=1800 kV USI= 1150kV Space required = 400 m² Space Required = 300 m²
25% space reduction
Test object
Divider
Chopping gap
Overshoot Compensat
ion
Impulse generator
Test object
Connectionpoint
Impulse generator
FACTORY TESTING - APPLIED VOLTAGE TESTING
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Applied Voltage Test IEC 60076-3, pos. 11
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Transformer based AC test system
- continuously duty cycle, high feeding power
- high test system costs
Resonant test system with variable inductance
- perfect sine wave, proven/robust technology
- less feeding power, less costs
Resonant test system with variable frequency
- perfect sine wave, proven/robust technology
- small components, lowest feeding power, best price
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Applied voltage test or separate source AC withstand voltage test can be performed with 3 different type of test systems
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Example of Applied Voltage Test for 1200 kV
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Test of transformer for 800 kV HVDC transmission at Siemens Nuremberg, Germany
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ADVANTAGES
Compact
Easy extendable
Low power consumption
Operates according to IEC >80% of rated voltage
Lower Investment cost
Applied Voltage Test – Variable Frequency Test System
Test system at Siemens Dresden, Germany
System Concept for Applied Voltage Test
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1 Control and feeding unit 2 Exciter transformer 3 HV reactor 4 Blocking impedance 5 Voltage divider
3
5
4
400V 50 kVA 50/60Hz
LV HV
Transformer to be tested
FACTORY TESTING - INDUCED AC VOLTAGE TESTING
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Generation of test frequency
Solutions for Induced Voltage test
Since the test voltage Up for the induced voltage test is often higher than twice the rated voltage, the test frequency must be at least doubled to avoid over-excitation of the iron core.
Motor / Generator Set Static Frequency Converter
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Induced AC Testing based on Static Frequency Converter
Different frequencies for loss measurement and induced voltage testing provided by static frequency converter – replacing several different motor-generator-sets
Fulfill all demands of standards
Efficient
Allows testing of transformers >1000 MVA
Expandable
Space-Saving
Easy to operate, intrinsically safe
ADVANTAGES
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Induced AC Testing based on Static Frequency Converter
Block diagram of transformer test system
Induced AC Testing based on Static Frequency Converter
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Transformer test system for induced voltage tests, based on static frequency converter, type WV 2000-4000/170
Static frequency converter build in
container Cooling system Step-up transformer High voltage filter
Induced AC Testing based on Static Frequency Converter
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Static Frequency Converter built in Container
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THD Value < 5%
Test voltage and current waveform – no-load loss measurement with THDu < 3.5% and THDi = 52% (150 MVA transformer)
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Sensitive PD Measurement
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PD Level < 10 pC according to IEC 60270
ON-SITE TESTING – SAME PRINCIPLE
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NO STANDARDS FOR ON-SITE TESTING
HIGHVOLT on-site test systems allow tests appropriate to standards of factory testing On-Site Tests: Applied Voltage Test Induced AC Voltage Tests Optional: Impulse Testing
HV On-Site Testing
ON-SITE TESTING – APPLIED VOLTAGE TEST
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Wide load range of power transformers 5 to 40 nF Variable test frequency 40 to 200 Hz Voltage 360 kV – Expandable to 720 kV Electric current 5 A
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Test System for Applied Voltage Test
Resonant system with variable frequency
Standard 40 foot trailer
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Applied Voltage – Procedure and Test sequence
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Transportation to site
Test arrangement and connection of test object (approx. 50 min)
Start system and enter test parameters (approx. 10 min)
Start automatic test sequence Automatic search of test frequency at 10% of U test
(frequency shall be not less than 80% of rated frequency per IEC)
Increase the voltage up to U test Withstand voltage test Decrease the voltage up to 0 V
Finish test and print test report (HIGHVOLT Suite®)
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Summary – Applied Voltage Test
Dielectric test of the main insulation (between winding and iron core/ tank; between the winding systems)
Test voltage up to 360 kV with additional reactor up to 720 kV
Required power supply: 400 Volt (3~), 40 kVA
Only one HV lead to connect the transformer under test
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ON-SITE TESTING – INDUCED AC VOLTAGE TEST
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Setup for Induced Voltage Test
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PD 1234
PLC
3 ~ 400V / 50~60 Hz
PD measuring system
HV capacitive compensation unit (Option)
Transformer to be tested
1234
1. Frequency converter 2. Step-up transformer 3. HV filter 1 4. HV compensation (Option) 5. HV filter 2 (Option) 6. Loss measuring system
1 2 3
4
5
6
Space for accessoiries
Design of Mobile Test System
Static frequency converter
Step-up transformer
Control room HV filter 1
Power supply cable, HV connection cable
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CT’s and VT’s
Space for accessories, HV electrodes, etc.
HV test lead
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Induced voltage – Procedure and Test Sequence (IEC/ IEEE/customer specification)
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1. Transportation to site
2. Test arrangement and connection of test object (approx. 50 min)
3. Start system and enter test parameters U test and f test (approx. 10 min)
Typically: U test = 80% of U test at factory f test approx. 2 x f rated (between f rated and 200 Hz)
Choose frequency of test = f test :
a) Factory test frequency i.e. 120 Hz,180 Hz, etc. b) Or to minimize the power demand choose frequency to take
advantage of variable frequency to reach self compensation
4. Start automatic test sequence
5. Measure PD at test voltage levels specified
6. Finish test and print test report (HIGHVOLT Suite®)
APPLICATION
Required for reactive power compensation during short-circuit tests, load-loss tests and on-load tap-changer tests
SOLUTION
Capacitor bank on one trailer or in one 40-foot container for single phase and small three phase types
Capacitor bank on 2 trailers in four 20-foot containers for larger three phase types (3 containers for capacitors, 1 for measuring transducers)
Standard types: - up to 250 MVA test objects: 36 kV / 24 MVA, HVCC 24000/36 - up to 500 MVA test objects: 36 kV / 54 MVA, HVCC 54000/36
Capacitor Banks for Mobile Transformer Test Systems
Principle sketch of mobile capacitor bank HVCC 24000/36
power measurement: current transformer / voltage transformer
CT1…CT3: phase current measurement CT4: protection against unsymmetrical currents
Compensation units can be connected to form a 3-phase or a powerful single phase capacitor bank
HV capacitive compensation units
40 ft trailer
cable drums
All transformers up to highest ratings can be tested on site
Higher power by mobile capacitive compensation banks is available
Mobile capacitor bank HVCC 24000/36 inside a 40ft container
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Output voltage: Up to 80 kV Output power: 1000 kVA / 620 kW
Power supply: 400 V (3~)
- 750 kVA mains supply or - 1200 kVA diesel generator Only 3 HV cables to connect the transformer under test
Easy set up: Within 1 hour ready to test
Summary – Induced Voltage Test
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EXAMPLES OF TESTED TRANSFORMERS
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Test of a 500 MVA Single Phase Trans- former in a Nuclear Power Station
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Test of 1phase main transformer with WV 620-1000/80
Power supply by mobile diesel generator
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Parallel connection of up to 3 test systems (total: 1.9 MW/3 MVA)
Parallel Operation for Testing up to 1200 MVA Transformers
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Summary
Testing power transformers up to 1200 MVA
According to IEC and IEEE standards
Waveform distortion THD < 5%
Partial discharge (PD) noise level < 10 pC (with 2nd HV filter)
Free adjustable frequency 40 to 200 Hz (self compensation)
Modular design allows for future expansion
Easy and fast test set up
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YOU DELIVER QUALITY OUR EQUPIMENT PROVES IT
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