New Techniques for the Monitoring of Transformer Condition

Transcription

1 New Techniques for the Monitoring of Transformer Condition Thomas Prevost OMICRON electronics USA IEEE T&D Conference Chicago, Illinois April 17, 2014

2 Agenda Monitoring Expectations & Needs Bushing Monitoring Capacitance Power Factor Transformer Monitoring Partial Discharge Voltage Transients Summary & Conclusions

3 Failure Rate Scope of Monitoring Expectations and Needs Classical 5a Diagnostics Temporary Monitoring Permanent Monitoring 3a time / a Continuous Diagnostics Condition based maintenance Full utilization of life span

4 Scope of Monitoring Expectations and Needs Arguments and user expectations > Continuous monitoring under service conditions Reliable measurement data > Diagnostic of errors before they appear Condition based maintenance > Knowledge about historical use Fully utilize life span of equipment

5 Transformer Failure Statistics [Viereck, Hillinger, Transform 2011]

6 Agenda Monitoring Expectations & Needs Bushing Monitoring Capacitance Power Factor Transformer Monitoring Partial Discharge Voltage Transients Summary & Conclusions

7 According to the data from various researches and electric power utilities, bushings failures make 5 to 50 %, or in average, one quarter of the total number of transformer failures.these failures most commonly cause transformer fires which may result in huge collateral damages of switchyard. Reference [3] indicates that 30 % of generator step-up transformer failures are caused by a bushing malfunction, and that they also cause 56 % of failures accompanied by fire.

8 Failure Mechanisms and Diagnostics Partial breakdowns Capacitance Partial discharges Voltage [kv] No. of layers % change E max = high A without layers E max = low with layers A

9 Dissipation Factor (%) Power Factor (%) Failure Mechanisms and Diagnostics Voids, cracks Partial discharges Capacitance Ageing by-products, moisture Dissipation factor / power factor 1,0 0,8 IEC60137 max: 0,7 % 1,0 0,8 IEEE C max: 0,85 0,6 0,4 0,2 0,0 typ: 0,25 OIP typ: 0,35 RIP 0,6 0,4 0,2 0,0 max: 0,5 typ: 0,25 OIP typ: 0,35 RIP

10 Where Can I Get the Reference from? Off-line test: Reference from HQ capacitor Im C R C X, I R I X I R I X u 0 (t) d U R (t) Z 1 Z 2 U X (t) j Uo Reference Measurement path On-line test: Reference?

11 Relative C/DF Measurement > Sum of the bushing currents > Three phase vectors are added up > Bushing-to-bushing comparison > Vectors of bushings in same phase are compared L1 L3 L2

12 DF (%) from to Systematic error 0.65 % plus instrument inaccuracy 0.5 % Capacitance? DF impossible! 1,0 0,8 Systematic error 0,6 0,4 0,2 0,0 typ: 0,25 OIP typ: 0,35 RIP [P. Picher Integration of New Transformer Monitoring Technologies... TechCon Asia-Pazific 2011] PAGE 12

13 Connection Diagram VT Reference U VT + 90 d I B j VT Bushing Data Storage and Analysis Unit

14 TanDelta Measurement Phase U Comparison to accurate off-line tests: DF E-3 C (pf) 467.1

15 Capacitance (pf) DF (%) C/DF Measurement over 1.75 Years 1,0 0,8 0.7 % IEC Warning 0,6 0,4 0,2 0,0 typ: 0,25 OIP RIP 0,27 +/- 0,05 % Measurement pf Warning 467 +/- 2 pf Measurement 400

16 DF Temperature Correction [ABB Guide for Bushing diagnostics and conditioning, Ludvika 2000]

17 Agenda Monitoring Expectations & Needs Bushing Monitoring Capacitance Power Factor Transformer Monitoring Partial Discharge Voltage Transients Summary & Conclusions

18 Reasons and Effects of Partial Discharges Reasons Failures of design or during manufacturing process Aging of equipment Electrical stress Thermal stress Mechanical stress Effects of PDs: Heating Creeping destruction of the insulation material Treeing, chain reaction Insulation breakdown, short circuit Treeing in polyethylene

19 Q in nc PD Activity over 4 Days 10 1 L1 L2 L :00:00 01:00:00 02:00:00 03:00:00 04:00:00 05:00:00 t in dd:hh:min

20 Fighting PD Noise: UHF Gating Corona Electr. PD Internal PD UHF PD EM Field

21 Combination of the Methods IEC UHF IEC PD Measurement & UHF PD Measurement Corrected IEC PD Measurement

22 3PARD: PD Discrimination by Amplitude Corona 1 MPD1 MPD2 MPD3 3 2 Internal PD EM Field

23 3PARD and Back Transformation

24 3FREQ: PD Discrimination by Spectrum A Corona 0.5M 0.5M 2M 8M f MPD1 8M 2M Internal PD EM Field

25 PD Risk Assessment Noise rejection Source separation Pattern classification PD localization Galvanic decoupling Gating UHF RTD 3 PARD 3 FREQ Manual Automatic Asset Phase Acoustic localization

26 Agenda Monitoring Expectations & Needs Bushing Monitoring Capacitance Power Factor Transformer Monitoring Partial Discharge Voltage Transients Summary & Conclusions

27 Switching Transients IEEE PES Transformers Committee Tutorial March 2014 Dr. Robert Degenneff

28 Voltage in kv Voltage in kv Switching Transients t in ms t in ms t in ms t in ms 29

29 Case Study: Combined Generator and Transformer Monitoring Generator 900 MW 21 kv GSU 1100 MVA Transmission line 400 kv 6 km Substation Grid 400 kv G UMTS Voltag Transformers Generator OMS843 - C/DF (Reference) PDM600 ca. 10 m OMS843 - PD - Transients - C/DF OMS843 - PD - Transients - C/DF Transformer 1 Transformer 2 UHF620 + UVS UHF620 + UVS

30 C/DF and PD Couplers Generator: Capacitive couplers Transformer: Capacitive bushing adapters and UHF drain valve sensor

31 U in µv P in dbm DF / % Monitoring Results 1,0% 0,8% UMTS U Voltage Transformers V W Generator 0,6% 0,4% OMS843 - C/DF (Reference) 1 Q IEC in nc 10 PDM600 0,2% 0,0% t in ms ca. 10 m OMS843 - PD --60 Transients - C/DF OMS843 - PD - Transients - C/DF 1 Transformer UHF620 + UVS UHF620 + UVS Transformer t in ms f in MHz 1000

32 dissipation factor in % temperature in C Influence of Environmental Conditions IEC60137 max: 0,7 % V-phase U-phase W-phase time / days

33 Voltage in kv Voltage in kv Transient Over-Voltages > Oszillation frequency 10 khz, beat frequency 600 Hz > Several times a day C Phase BAT20 Generator 900 MW 21 kv G GSU 1100 MVA Transmission line 400 kv 6 km Substation Grid 400 kv B Phase A Phase t in ms BAT10 BAT t in ms t in ms 18

34 Agenda Monitoring Expectations & Needs Bushing Monitoring Capacitance Power Factor Transformer Monitoring Partial Discharge Voltage Transients Summary & Conclusions

35 Summary On-line monitoring as future trend C/DF monitoring The reference problem Solution: VT reference Accuracy +/- 2pF On-line PD monitoring The noise problem Possible solutions: UHF-gating Software separation Pattern recognition Voltage Transients

36 Questions?? Thomas Prevost