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PD Testing Some Perspectives from Users
Josh Perkel and Nigel Hampton NEETRAC
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Outline How often is PD testing used by Utilities?
What are the ways PD is used HV/EHV & MV Why do so few Utilities use PD? Complicated No consensus Confidence in Diagnosis Value / Benefit Drives Unexpected Practices
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Cost Chain – cable system
FIRST COST Cable Materials Metallic Non-metallic Cable Production Delivery Cable Construction Installation Maintenance Repair Lost power End Of Life Accessory Materials Metallic Non-metallic Accessory Production Delivery Accessory Construction Installation Health Commissioning How often is PD testing used by Utilities
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Ways the PD Tests are Used by Utilities
System Commissioning Health of Aged Systems As part of the project handover / acceptance Part of a coherent program Opportunistically funded Pilot Study Management Directive Part of a coherent program Opportunistically funded Pilot Study Management Directive How often is PD testing used by Utilities
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Outline How often is PD testing used by Utilities?
What are the ways PD is used HV/EHV & MV Why do so few Utilities use PD? Complicated No consensus Confidence in Diagnosis Value / Benefit Drives Unexpected Practices
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What has Failed? Collated in 2014 ICC Sub A Fall 2015
How often is PD testing used by Utilities – HV/EHV
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Bathtub Curve - Times of Failure
Shape Parameter = 0.3 Infant Mortality Shape Parameter = 1 Random ICC Sub A Fall 2015 How often is PD testing used by Utilities – HV/EHV
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Use of PD HV/EHV CIGRE B1.28 How often is PD testing used by Utilities – HV/EHV
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Why use PD – HV/EHV CIGRE B1.28
How often is PD testing used by Utilities – HV/EHV
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No reported use of PD Only
Evolution at HV & EHV HiPot Only HiPot with PD No reported use of PD Only CIGRE B1.28 How often is PD testing used by Utilities – HV/EHV
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Outline How often is PD testing used by Utilities?
What are the ways PD is used HV/EHV & MV Why do so few Utilities use PD? Complicated No consensus Confidence in Diagnosis Value / Benefit Drives Unexpected Practices
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PD use MV in Utility Distribution programs
CDFI How often is PD testing used by Utilities - MV
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PD use MV in Nuclear Plant programs
90% CI Concerns over neutral degradation Practitioners How often is PD testing used by Utilities - MV
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CDFI / NEETRAC Experience
Experience Base 10 Utilities 50 Test Locations >1,120,000 ft Optimal opportunities for utilities to see different diagnostics at work on their system
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Outline How often is PD testing used by Utilities?
What are the ways PD is used HV/EHV & MV Why do so few Utilities use PD? Complicated No consensus Confidence in Diagnosis Value / Benefit Drives Unexpected Practices
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PD Tests are Complicated
Difficult to employ Access Crews Equipment Time Neutrals Impenetrable Interpretation If we don’t understand how it is done how do we know it is done consistently Black Box / Proprietary Methods Expedient Interpretation PD tests become increasingly problematic as more of the neutral corrodes Why do so few Utilities use PD - Complicated
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PD Tests are Complicated
Difficult to interpret Tests on “Components in Factories” ≠ “Test on System in Field” Apart from new installations, no clear metric of severity: Number Magnitude Level Location Evolving PD Test Levels Factory Tests Physical Dimensions Electrical Routine AC Hipot AC Hipot PD PD Why do so few Utilities use PD - Complicated
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Unexpected Outcomes Not so unexpected! Certainly complicated!!
The ones that were identified as critical: “Never failed” “Were fine when I took them out and dissected them” “The ones that were identified as less critical failed way before the ones that were most critical” Within 5 yrs expect: 0-1/3 very bad to fail 0-1/7 bad to fail 2-3/90 acceptable to fail Old Accessories / Cable % failing in 5 yrs PD shows acceptable 3 PD shows bad 10 PD shows very bad 25 Not so unexpected! Certainly complicated!! Why do so few Utilities use PD - Complicated
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Outline How often is PD testing used by Utilities
What are the ways PD is used HV/EHV & MV Why do so few Utilities use PD Complicated No consensus Confidence in Diagnosis Value / Benefit Drives Unexpected Practices
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Drives Unexpected Practices
Currently: Longevity / Reliability comes from following training / instructions Dielectric Connector Jacketing Evolves to: Passing a test Outcome: Develop methods / skills to pass the test, which may only address one element Why do so few Utilities use PD
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Outline How often is PD testing used by Utilities?
What are the ways PD is used HV/EHV & MV Why do so few Utilities use PD? Complicated No consensus Confidence in Diagnosis Value / Benefit Drives Unexpected Practices Not presented - - Lack of Time
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Conclusions PD tests deployed on MV and HV/EHV for different reasons and at different times in the life cycle now routine at HV/EHV – presence & approx locn of PD is paramount Complication is higher for PD as compared to other diagnostic techniques employed by utilities Interpretation is difficult – no clear way of assessing severity Different embodiments – voltage sources, bandwidth, etc. Technologies continue to evolve Value/Benefits can be estimated using probabilistic principles Have to be comfortable with ranges / imprecise outcomes Benefits are driven by sizeable Intangible costs PD is a useful tool in the cable diagnostic toolbox 22
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