B.1.1.4 Cable jointing and testing

Who supplies them

In house by cable manufacturers.

Independents: Maillefer, Power CSL and WT Henley.

Key facts

There are two types of joints:

• The factory flexible joint connects individual segments of cable core into one continuous length during the lay-up process. Crucially, the joint must have the same electrical, mechanical and thermal properties as the rest of the cable and result in a joint that it does not hamper installation or increase the risk of cable failure.
• The field rigid joint is a manufactured product. It may be supplied to the wind farm owner or the offshore transmission owner (OFTO) with the cable in case of failure during operation or supplied as a planned joint to link sections of the export cable.

Field rigid joints have generally been bespoke products because of the substantial variations in cable design between wind farms. There is growing interest, particularly by OFTOs, in developing joints that are suitable for a range of designs.

Cables undergo a series of tests before dispatch, dependent on the cable type and voltage class, including:

• Cable (and accessories) pre-qualification tests
• Cable (and accessories) type tests
• Cable routine electrical tests on each manufacturing length before jointing and armouring 
• Sample tests 
• Routine factory splice tests, and
• Tests on complete cable lengths including factory installed joints (if any).