The 5 Factors To Assessing Cable Splice Life Expectancy

Published 04 May 2021

Cable Splicing

Assessing Life Expectancy

Guest Article | 3M Electrical Canada

Thorne & Derrick Stockists & Distributors for 3M Electrical Since 1985

Scotchcast, Scotch & ColdShrink Joints, Terminations up to 66kV Ex Stock

Cable splice failures are expensive, so just imagine the dire consequences of a power failure leaving over 700,000 customers without power. Many of us in Ontario can still recall the shock of the 2003 Northeast Blackout.

As a consumer of electricity our expectation is that our lights stay on, our fridges stay cold, and our roads stay safe with operating traffic lights. When the lights go out, utilities have the extensive task of finding the source of the electrical or power cable fault, communicating with public and customers, and taking on the cost of repair including labour costs.

How do utilities actively try to prevent electrical failures?

Utilities measure system average interruption duration index (SAIDI) and customer average interruption duration index (CAIFI) as both of these are negatively impacted by underground cable splices and their failures. They are constantly looking for ways to help improve these measurements – and improvement comes down to choosing safe and reliable MV Cable Accessories.

Identifying this need within the utility industry, I created a Whitepaper that evaluates the five critical factors to help determine the overall life expectancy of a cable splice. I did this by leveraging 3M Cold Shrink QS-III’s 23 years of field experience.

➡ Did you know: Some of the 3M Cold Shrink Products installed in the field are still operational after almost 50 years!

The goal of this study is to help provide utilities with research and insights to help improve their SAIDI and CAIFI measurements.

Study highlight: 5 factors to help determine the life expectancy of an electrical Cable splice

1. Technology: Reliability of an electrical cable splice hinges on your ability to maintain radial splice pressure on the cables. 3M™ Cold Shrink QS-III is equipped with 3M™ Cold Shrink Technology, which retains radial pressure over the life of the cable splice. As a result, there is no loss of pressure with heat cycling.
2. Materials: Elasticity and the capability to apply in cold environments (especially in Canada’s frigid winters) are critical. 3M™ Cold Shrink QS-III’s silicone rubber is an excellent material choice for splicing applications. It acts as a “living seal” – helping provide long-term elasticity (including at negative temperatures) and has great electrical properties required by a robust splice design. Additionally, we use silicone rubber filled with thermally conductive additives to help improve heat dissipating properties of the splice body.
3. Design: An electrical cable splice or cable joint must be designed to manage electrical stresses by minimizing them for increased long-term performance. 3M™ Cold Shrink QS-III’s moulded splice body exhibits design features that lower electrical stresses. The features include large electrical geometric stress cones, rounded semi-conductive electrodes with an undercut insulation that lower stresses at cable/splice interface and additional insulation thickness at the end of the inner electrode to compensate for increased stresses in this area.
4. Workmanship: Workmanship in splice installation and cable preparation have a great impact in long-term performance. A clear majority of cable failure investigations that I’ve run for our customers pinpoint poor workmanship in cable preparation techniques as the leading root cause for failures. Some of the negative impacts of inconsistent cable preparation and/or cable cleaning that increase electrical stresses can be mitigated by design features such as the rounded semi-conductive electrode with an undercut of insulation that lowers stresses in the area of the splice/cable interface.  3M™ Cold Shrink QS-III is designed to help mitigate these cable preparation errors and the moulded electrical splice body offers ease of installation and high quality.
5. Testing Procedures: A product that is designed and tested at levels meeting and exceeding industry standards will have an adequate long-term performance. For 3M™ Cold Shrink QS-III qualification testing, we rate our electrical splices one basic insulation level (BIL) level higher than the corresponding splice classification (ex. 15kV splices meet the BIL requirements of a 25kV splice).

Further Reading

• Cable Terminations | Cold Shrink Terminations MV HV Cables
• 3M Cold Shrink Terminations Connecting Nexans 12kV (MV) Cable Onto Busbar
• 66kV Terminations | NEW Stock Introduction for 3M Cold Shrink Cable Terminations
• 3M Terminations | Surface Tracking on Medium Voltage Cable Terminations by 3M

THORNE & DERRICK

T&D are Specialist Distributors to UK Distribution Network Operators (DNO’s), NERS Registered Service Providers, ICP’s and HV Jointing Contractors of an extensive range of LV, MV & HV Jointing, Earthing, Substation & Electrical Equipment – this includes 11kV/33kV/66kV joints, terminations and connectors for both DNO and private network applications.

Contact our UK Power Team for competitive quotations, fast delivery from stock and technical support or training on all LV-HV products.

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