Verifying MV Cable Sheath Integrity

Published 18 Aug 2020

Republished with the Kind Permission of Sam Soady |

Eccentricity Pty Ltd Director /HV Operator / Cable Jointer

Verifying MV Cable Sheath Integrity

As a cable jointer, most of the time I am called in to jobs at specific times during construction to complete high voltage cable terminations.

I usually only see the end stages of most projects, and the HV cables have already been installed by other contractors.

As the cable jointer and electrician certifying the cable installation, it is important to verify the cable has been installed appropriately. As the cables are generally buried direct underground or in conduit systems, it can be difficult to inspect the cable for physical damage that may have occurred during installation.

This is when a sheath integrity test should be performed. Eccentricity recommends testing the sheath integrity prior to installation (on the cable drum) and post installation (in the ground). This gives you a good baseline to compare to after the cable has been installed and whether damage has occurred during installation.

Potential hazards that can damage the MV cable sheath include:

Binding machinery that wraps single core cables to tightly into trefoil
Rocks / debris present in the underground trench
Sharp edges along the route of installation
Not using suitable aggregate material or sand when backfilling around cables

Image courtesy of Eland Cables

The sheath integrity test consists of a DC voltage injection on the screen wires of generally 1000V on MV cables to the general mass of earth. By proving the insulation resistance of the outer sheath is acceptable, it can be expected no damage to the outer sheath has occurred during installation.

Before Eccentricity completes any terminations for our clients, we complete this sheath integrity test to further ensure the baseline of the cable installed is adequate and the termination has not compromised the sheath in any way.

About Eccentricity

Eccentricity is a specialised Brisbane based company with a team of dual trade electricians and cable jointers. Our technicians are fully qualified to work on cables up to 66kV, including XLPE, PILC and EPR cables, backed by over a decade of industry experience.

With a modern and fully compliant fleet of industry vehicles, we are capable of accessing any high risk environment to perform works with a wide range of major MV HV cable jointing projects including, mining, oil, gas, renewable energy, and high voltage transmission networks.

Eccentricity has the capacity for small or large scale projects, providing reliability of power networks wherein client satisfaction is a top priority. We provide a high level of quality with all aspects of both installation and commissioning, ensuring we comply with all relevant regulations and legislative provisions.

Experts In Equipment for Explosive Atmospheres with ATEX & IECEx Certification

Specialist Suppliers of High Voltage Electrical Equipment & Cable Accessories

Jointing, Earthing, Substation Electrical & Safety Equipment Distributors

Thorne & Derrick International are specialist distributors of LV, MV & HV Cable Installation, Jointing, Duct Sealing, Substation & Electrical Equipment – servicing UK and global businesses involved in cable installations, cable jointing, substation, overhead line and electrical construction at LV, 11kV, 33kV and EHV.