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