Cable Accessory Failure Analysis


Cable Accessory Failure Analysis
Cable Accessory Failures,
Contributing Factors, and Steps
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
Cable Accessory Fundamental
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
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
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
Immediate Outcome
Worked with suppliers to simplify instructions,
with clear, colorful illustrations
Splice kits assembled and limited to specific
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

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