Introduction

Insulation failure of distribution cables causes interruption to the network, typically, in the form of power dips disturbance for the national 22kV ring network system and momentary outages in 6.6kV open ring network, whom the latter can be restored through remote switching. There were cases of cables having passed IR tests but failed in service subsequently.

Objective

This research project aims to:

• Enhance cable insulation (IR) test guidelines to international best practices.
• Develop methodology and data analytics software using historical and new IR test records to generate on-site assessments under IR test enhanced guidelines.
• Further, enhance cable insulation health on-site assessment and cable repair prioritisation with additional cable diagnostics tests coupled with data analytics software to ensure the only healthy cable is energized into the network.
  

Methodology

Besides looking at the assessment methodology to ensure that cables put into service will not fail, the research will also be looking at the degradation of cables at the insulation level. This would correlate the degradation effects against the insulation testing results and the corresponding failure modes.

Outcome

Enhanced cable insulation (IR) test guideline, demonstrated by:

• Health trending assessment with historical IR values.
• Benchmarked against international best practices.
• Identify follow-up actions based on enhanced guideline.

Cable insulation health assessment software that includes data analytics for trending historical cable IR test results and additional cable diagnostic tools, which is an improvement over the existing single IR test:

• Insulation resistance (IR) test
• Polarisation index (PI) test
• Dielectric absorption ratio (DAR) test
• Dielectric discharge (DD) test
• Step voltage (SV) test
• Ramp test (RT)

The outcome of this research project will improve not only the current cable IR test guideline but, more importantly, assess the cable insulation health accurately and its suitability for energization using on-site assessment software. Thus, it will help to reduce any unexpected cable failure, associated impact from the outage, and consequentially increase the long-term reliability of the power delivered.