Case 4 - Problems Of Cable Joint Earth Continuity On Low Voltage Feeder Cable

By Chris Dodds on 3rd February, 2015

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Case 4 - Problems Of Cable Joint Earth Continuity On Low Voltage Feeder Cable

LV HV Heat Shrink Cable Joints & Cable Terminations. Fault Analysis.

T&D have an obligation to investigate any cable joint or cable termination product failure, but over the years we have been asked more and more to get involved in general cable failure analysis for low voltage LV and high voltage HV networks.

This Blog is Part 4 in a series of 5 covering Cable Fault Analysis linked to the cable jointing and terminating of high voltage power cables.

Case 1 - An 11kV 3 Core Transition Cable Joint Which Was Audibly Discharging

Case 2 - High Voltage Cable Joint Failure On 11kV Trifurcating Transition Joint

Case 3 - An 11kV Heat Shrink Transition Cable Joint Failure

Case 5 - "Buzzing" 11kV Cable Box Terminations On XLPE 3 Core Cables

Case 4

An oil company was having problems with the earth continuity of a low voltage feeder. 

The problem was narrowed down to a LV low voltage heat shrink cable joint installed between 15-20 years previous and manufactured by a company no longer in business.

On investigation it was obvious the material had not reacted well to the years of hydro-carbon attack. The butyl mastic inner fill had turned to a sticky paste and the inner, connector insulation tubes, had also suffered. The cause of the earth continuity problem was due to poor connections onto the wire armours and subsequently, liquid rubber isolating the armours from the earth continuity lead.

Even though the heat shrink joint used was not designed to withstand these conditions, it had survived remarkably well, and only failed as a result of hydro carbons, entering the cable some distance away and travelling between the wire armours and inner sheath to the cable joint, and finally attacking the heat shrink cable joint from within.

Invitation

Thorne & Derrick are inviting you to join LinkedIn’s fastest growing Discussion Group : Low & High Voltage Power, Cabling, Jointing, & Hazardous Area Electricals (LV-HV).

Discussion subjects include cable installations, cable jointing, electrical substation, overhead line and electrical construction at LV, 11kV, 33kV and EHV.

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Category:  HV Cable Jointing & Terminating

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