On-Line Partial Discharge Testing Skip Hicks Director - New Business Development What Is Partial Discharge? z According the the International Electrotechnical Commission (IEC) International Standard 60270, Section 3.1 published in 2000, the definition of Partial Discharge is: “Localized electrical discharge that only partially bridges the insulation between conductors and which can or cannot occur adjacent to a conductor.” IEC 60270 Section 3.1 Notes z z z “Partial discharges are in general a consequence of local electrical stress concentrations in the insulation or on the surface of the insulation…” “Corona is a form of partial discharge that occurs in gaseous media around conductors which are remote from solid or liquid insulation…” “Partial discharges are often accompanied by emission of sound, light, heat, and chemical reactions…” Paper -Insulated Lead Cable Paper-Insulated Extruded MV Cable Construction EPR Cable Construction Jacket Shield SC* Strand Screen_* *Insulation Conductor EPR Insulation in Cable Accessories z Most Pre-Molded Cable Terminations, Stress Cones and other Cable Accessories are manufactured from an EPR compound because of it’s great resistance to treeing and the effects of corona discharge around terminations and splices Types of Cable Failures z z z Laminar Insulation Failures Voltage Stress Related Failures in Extruded Insulation Cable Accessory Failure Laminar Cable Insulation Failure Picture Provided By Pirelli Wire Laminar Cable Insulation Failure Picture Provided By Pirelli Wire Tape removed showing electrical treeing Final Partial Discharge Report The data is then used to electronically generate a final report that details the severity and location of partial discharge activity PD activity is then classified into the following category(s) and appropriate recommendations made Severity Level Classifications Level A-Low levels of Partial Discharge activity occurring No necessary actions at this time Retest in years Level B-Moderate levels of Partial Discharge activity occurring Retest within 12-18 months to monitor & trend PD activity Level C-High levels of Partial Discharge activity occurring Prioritized repair or replacement is recommended Final Partial Discharge Report z z z Software has been developed for pattern recognition and conversion of data to usable format Software significantly reduces the amount of time required to generate a final report Reports can show the severity level of any observed partial discharge activities, where they are located, recommended testing intervals, other recommended actions, etc In addition, the final report can provide the actual data used to formulate our recommendations Partial Discharge Analysis z z All data recorded while on-site is scrutinized to uncover any pending problems within the tested system, and analyze their severities and locations A comparative analysis is generated from the data gathered while on-site This comparative analysis allows for prioritization/planning of cable replacements, scheduling repairs, etc Success Stories z Michigan Department of Corrections - St Louis Correctional Facility – Tuesday - Identified “Level C” Y-Splice located in PMH feeding 5KV Padmount Transformer Recommended Prioritized Replacement – Friday - Y-Splice violently fails before facility could replace causing unplanned outage • 5KV Distribution System was less than years old and failure determined to be workmanship related on the YSplice Success Stories z Michigan Department of Corrections Bellamy Creek Correctional Facility – Performed On-Line Partial Discharge Testing to establish baseline data for facility upon completion of Acceptance Testing – 15KV Distribution System Passed Acceptance Testing that consisted of AC High Potential Testing – On-Line Partial Discharge Testing found a workmanship defect at a Transformer Termination which was not found by High Potential Testing Success Stories z Disneyland Resort – Performed On-Line Partial Discharge Testing to evaluate condition of 30 year old 1000 ft 5KV XLPE WTF Feed – Testing was performed during normal plant production with zero down time – Discovered severe electrical treeing throughout 100 ft length of feed – Facility scheduled replacement with zero impact on Resort Operations Success Stories z General Motors – Performed On-Line Partial Discharge Testing to prioritize repair/replacement of 35 year old XLPE Cable and accessories – Testing was performed during normal plant production with zero down time (August 2002) – Identified “Level C” splice located in Tap Box on roof of facility Repairs were not scheduled until July Outage 2003 – Cable Splice failed Dec 2002 causing 48 hr loss of plant production Success Stories z Primcor Refinery - Lima, OH – Performed On-Line Partial Discharge Testing to determine condition of 34.5KV Distribution cables and accessories – Testing was performed during normal plant production with zero down time – Several areas requiring prioritized attention were identified – Replaced pothead connection with attached results Primcor Refinery - 8/2002 (Initial Test) Primcor Refinery - 8/2002 (Initial Test) Primcor Refinery - 2/2003 (After Repairs) Primcor Refinery - 2/2003 (After Repairs) Customer List z General Motors z Primcor Refineries z Ford Motor Company z Daimler-Chrysler z IBM z Denver County z Exxon Mobil z State of Michigan z Arizona Public Service z LCCC z Phelps Dodge z SCCC z Disney Resorts z Kinder Morgan z Salem Electric z Visteon z Raytheon z Ineos Fluor Chemical z Georgia Pacific z Boise Cascade z Weyerhaueser z Entergy z Motorola z Others… Summary z z z z On-Line Partial Discharge Testing is a noninvasive, non-destructive, predictive test procedure Testing is performed while plant remains on-line, completely eliminating the need for an outage Two part process consisting of both on-site data gathering and off-site system analysis Final report generated which provides interpretations and recommended actions References [1] S.A Boggs, R.J Densley, “Fundamentals of Partial Discharge in the Context of Field Cable Testing”, IEEE Electrical Insulation Magazine, Vol 16, No [2] S.A Boggs, R.J Densley, and J Kuang, “Mechanism of Conversion of Water Trees to Electrical Trees under Impulse Conditions”, IEEE Trans PD-13, No 2, April 1998, pp 310 - 315 [3] H Hu, “Evaluation of Discharge Resistance of Solid Dielectric Power Cable Insulations”, IEEE Electrical Insulation Magazine, Vol 11, No [4] Dr M Brown, “EPR-Based URD Insulation - A Question of Confidence”, IEEE Electrical Insulation Magazine, Vol 4, No [5] R DiLorenzo, F Krajick, S Boggs, J Ronzello, G Pehlert, R Dharmarajan, G Fridland, R Annicelli, “Comparison of AC Impulse Breakdown of Model EPR and TR-XLPE Cables as a Function of Wet Electrical Aging”, PES ICC, April 2002 [6] Boggs, S.A “Mechanisms for Reduction of Impulse Strength Resulting from Small Water Trees” 2000 Annual Report of the IEEE Conference on Electrical Insulation and Dielectric Phenomena pp 547-551 (also submitted for review to Trans PD.) [7] C Laurent, C Mayoux, “Limitations to PD as a Diagnostic for Deterioration and Remaining Life”, IEEE Electrical Insulation Magazine, Vol 8, No [8] F.H Kreuger, M.G Wezelenburg, A.G Wiemer, W.A Sonneveld, “Errors in the Location of Partial Discharges in High Voltage Solid Dielectric Cables”, IEEE Electrical Insulation Magazine, Vol 9, No [9] S Boggs, J Xu, “Water Treeing - Filled vs Unfilled Cable Insulation”, EIRC ... cable system Partial discharge test results can be trended over time Unlike traditional High Potential Testing, partial discharge testing is not destructive to an insulation system (Hipot testing. .. operating conditions z z z z Partial discharge testing is a PREDICTIVE qualitative analysis tool that can warn of a potential upcoming system failure The Partial Discharge testing program can locate... 5 5 Historical Testing Methods z Off-Line Testing Techniques – High Potential Testing – Power Factor/Dissipation Factor Testing – Very Low Frequency Testing (VLF) z In-Service Testing Techniques