Cable Accessory Failure Analysis
Transcription
Cable Accessory Failure Analysis
Cable Accessory Failures, Contributing Factors, and Steps Forward RPM Brasil 2015 Joseph H. Groeger Mantis Associates, Inc. Presentation Scope • Focus primarily on modern splices and accessory designs (past 25 years) • Addresses corrective actions to reduce present failure rates experienced in the field Cable Accessory Failure Analysis • Critical step toward maintaining and improving system reliability • Provides understanding for what is failing and how to improve: • Standards and product selection • Training and field practices Failure Analysis Overview • Review component design to determine how it should work, then objectively investigate failure reason • Primary reasons for failures: • manufacturing or installation defect • aging-related degradation • improper component selection • poor design/materials Thousands of Case Studies 12 North American Utility Companies • Heat-shrinkable splices • Pre-molded EPDM rubber splices • Pre-molded silicone rubber splices • Pre-molded EPR splices • Cable accessories • Oil/paper/lead cables not included Practical Limitations • Failure data by many companies collected in field and not a priority • Splice and accessory failures often identified as cable failures • Independent or dedicated failure analyses important • Field practices must be witnessed in non-invasive manner Cable Accessory Fundamental Expectations • maintain conservative electric stress distribution • prevent moisture penetration • not serve as the weak link in a cable system • You pay for and expect a well developed product that should perform for 40+ years Historical Review of Accessory Age and Failure Cause • 0 - 1 year: major installation errors • 1 - 5 years: installation errors, water penetration • 5 - 20 years: materials defects, internal corrosion, external factors • 20 + years: dielectric breakdown, thermal aging Accessory Failures by Year Per 1000 Installed Two Utility Companies limited to devices aged 1 year or less Troubling Trend in Recent Years • Increase in early failures • Failure analyses indicated frequent basic problems • Increase in accidents • Corrective actions required Review of Failures and Field Installations Some Errors Major and Hard to Understand Cable Connectors As They Should Be…. Internal Assembly Errors… More Assembly Errors… A Significant Pattern of Errors Pattern of Pre-molded Elbow Failures Field Survey Methods • Example: 2500 recent termination installations on ALL network transformers and 1100 multi-way Vista switches • Assembly errors indicated • AM radio (440 kHz - 1700 kHz) used to survey for electrical noise, combined with visual examination • 300 bad assemblies replaced (12%) Investigation of Underlying Problems • Experienced crews recalled to assemble accessories in classroom • Inexperienced crews asked to follow accessory installation instructions • Crews often confused when asked questions about instructions • Engineers confused by instructions Really??? Immediate Outcome • Worked with suppliers to simplify instructions, with clear, colorful illustrations • Splice kits assembled and limited to specific applications • Cable accessory packaged with proper connector • Measurement templates included Future Goals • Simplify cable accessory installation instructions and move to tablet format • Include check list that generates a work record • Include reference photographs in addition to illustrations and ‘good’/‘bad’ examples • Include reference library for support in field Thank You