I.5.6 Electrical testing and termination

Function

The electrical testing is designed to test and prove cable integrity whilst the termination enables the electrical connection between the offshore cable and either the wind turbine, the substation or the onshore cables.

What it costs*

About £9 million for a 1 GW offshore wind farm.

Who supplies them

The electrical testing and termination is usually provided by the cable installation contractor (see [I.5]).

Manufacturers of electrical testing equipment and termination tools: 360 Wind, Axess Group, Baur, JDR, Megger, Pfisterer, Tekmar, V&SH Offshore and WT Henley.

Key facts

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

• Cable (and accessories) pre-qualification tests and type 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).

Terminations are made after the cable has been pulled into the offshore substation or floating substructure. The armouring and insulation of the cables is stripped back and the cores are connected to a termination plug. The plug is then interfaced into a designated junction box or switchgear using a connector. A similar procedure is conducted for the fibre optic cable.

Terminating high-voltage cables is a highly skilled process that takes time to learn.

Prior to making terminations, a series of electrical tests are performed to prove the cable’s electrical integrity. These include low frequency tests, insulation resistance tests, time-domain reflectometry tests and optical time-domain reflectometry.

After the cable is pulled into the transition joint pit on shore, it is connected to the onshore portion of the export cable.