(other than Historical PD Tests) )

Transcription

1 Diagnostic Testing Techniques for Distribution and Transmission Cables (other than Historical PD Tests) ) Experience with available techniques ICC Education Session - May 2011 Nigel Hampton, Josh Perkel NEETRAC ICC Education May

2 Learnings Diagnostic Process, more than a measurement Simple Withstand & Monitored Withstand Context isolated tests versus patterns Evolving content Correlation with Service Performance ICC Education Session - May

3 Withstand Many Approaches Dielectric Loss Leakage Monitored Withstand ICC Education Session - May

4 What is the Diagnostic Process Measurement Criteria Check Reporting & Archiving ICC Education Session - May

5 Withstand Test Process oltage EARLY Hold Entry HOLD The goal is to have circuit out of service, test it such that imminent service failures are made to occur on the test and not in service Voltages and Times for VLF covered in IEEE Std Ramp Entry t = 0 t Test Time ICC Education Session - May

6 Length Adjustments Comparison of withstand failure on test rates must include length adjustments. 1,900 ft. Choose an appropriate base length ICC Education Session - May 2011 Dielectric Withstand6

7 Length Adjustments Comparison of withstand failure on test rates must include length adjustments. 1,900 ft. Failure 500 ft. 500 ft. 500 ft. 400 ft. Censored Dielectric Withstand ICC Education Session - May

8 Collated Experience segments] s on Test [% of 1000 ft Subset of 2800 miles of the 9800 miles in total for VLF where we have length data 3.7 % 2.7 % 2.0 % Failure 1 10 Time on Test [Min] 100 ICC Education Session - May

9 Test Performance for Different Utilities of 1000 ft. Segments] on Test [% Utility A1 A2 D H I 1000 ft Length Adj. VLF Simple Withstand Tests 35.5% 4.3% 3.5% 3.2% 0.2% Failures Time on Test [Minutes] ICC Education Session - May

10 Care required with experience VLF Simple Withstand Tests ICC Education Session - May

11 Performance After Test Pass/No Pass Service Failur res [% of Tes sts] Test Result Pass FOT 1.8 Uo, 30 minutes VLF Simple Withstand Tests 28.3% 3.2% 1 2 Years Time [Days since Test] 1000 ICC Education Session - May

12 Monitored Withstand Test Protocol Voltage Ramp HOLD Time ICC Education Session - May

13 Ways Not to Pass a Monitored Withstand Failure Insulation puncture OR High Dielectric Loss OR High Instability Measured by standard deviation in consecutive measurements at one voltage level ICC Education Session - May

14 Tan δ and Stability 1000 VLF Monitored Withstand Tests Withstan nd TD (1E-3) Result 1 No Pass - Tan Delta No Pass - Monitored Withstand Pass - Tan Delta & Withstand Withstand (1E-3) ICC Education Session - May

15 Monitored Withstand Results 7.9% No Pass - Tan Delta No Pass - Monitored Withstand Pass 10.9% 81.2% Voltage Ramp Tan δ Monitored Withstand Tan δ Time ICC Education Session - May

16 Simple Withstand Results On a 1000ft basis 98.5% survive 1.5% fail 6.1% F ailures in Simple Withstand Mode Surv iv ors in Simple Withstand Mode 93.9% 9% Voltage Simple Withstand Time ICC Education Session - May

17 Failures 60 Failu res per Yea r on PILC Sy stem Est Pre Diagnostic Start Up Implementation Combined Diagnostics ICC Education Session - May

18 Monitored Withstand VLF & Tan Delta Ramp Stability Std Dev Tip Up Level Hold Trend Size, Slope Stability Std Dev Level VLF & UWB PD Ramp? Hold?? = Magnitude, Inception, t/f Map Coordinates, Features, Location ICC Education Session - May 2011

19 Combined Diagnostics - Monitoring DAC UWB PD Dielectric Loss Estimates VLF Tan Delta UWB PD Tan Delta [1e-3] Tan Delta PD Pulse Count PD Pulse Rate [#/5 min] Time [min] ICC Education Session - May 2011

20 Dielectric Loss Test Process oltage Measures total cable system loss (cable, elbows, splices & terminations). May be performed at one or more frequencies (dielectric spectroscopy). May be performed at multiple voltage levels. Loss measurement Time ICC Education Session - May

21 Measured Tan δ data from Cable Systems PILC XLPE [E-3] TD Voltage [kvrms] Measurement Sequence ICC Education Session - May

22 Tan δ at U 0 Tan Uo (1e-3) ID FDR 2-1 FDR 2-2 FDR 2-3 FDR 2-4 FDR 2-6a FDR 2-6b FDR 2-7a FDR 2-7b 10 8 ICC Education Session - May

23 Tan δ and Tip Up Map Tan Uo (1e-3 3) ID FDR 2-1 FDR 2-2 FDR 2-3 FDR 2-4 FDR 2-6a FDR 2-6b FDR 2-7a FDR 2-7b Adjacent phases are different Tip Up {1.5Uo-0.5Uo} (1e-3) 10.0 ICC Education Session - May

24 Jacketed & Unjacketed XLPE Data Christopher's Coves Wimbledon Woods Failures Uo Uo Tip Up Uo ICC Education Session - May

25 2010 versus 2007 Results Uo Uo Tip Up Mean Uo ICC Education Session - May

26 Jacketed & Unjacketed Data Changed Changed for the Worse Poor rer Tip Up 1 Changed for the Better No Change 3 6 Changed 1 2 ICC Education Session - May 2011 Poorer Tan Delta Three Action Required failed before testing in 2010

27 Criteria Assumption of unusualness based on the 80th & 95 th percentiles Pe ercent Tip Up of Tan Delta between 1.5 Uo & 0.5 Uo (E-3) Ins Class Filled Paper PE Evolution is sensitive to the acquisition of new data especially data on poorly performing circuits ICC Education Session - May 2011

28 Relationship to Performance in Service Failur res of PE Bas sed Insulatio ons (%) Overall Class No Action Required Further Study Action Required PE based cables Elasped Time Feb 2011 (Month) ICC Education Session - May

29 Problems in the Monitor Phase Requires time you cant implement your diagnostic straight out of the box Requires utility discipline Accurate monitoring and communication in the field Hands Off approach Requires that you get the selection correct The area has to be bad enough You have to have enough Sufficient diversity ICC Education Session - May

30 Some general reflections 1. A database of field failure diagnostic data shows that diagnostic techniques can provide useful. 2. Diagnostic results can be imprecise, diagnostic are generally beneficial. 3. Benefits can generally be quantified, but takes time and effort. 4. HAVE to act on ALL replacement/repair recommendations to get improvements. 5. It is difficult to predict whether or not the problems/defects detected by PD or Tan δ will lead to failure. 6. Tan δ & PD measurements require interpretation to establish how to act. ICC Education Session - May