Offshore after-laying, maintenance and diagnostic testing of power cables

Off-shore Wind Farms (OWF)

Submarine cables play a crucial role in bringing generated power to off-shore substations and finally to the substations on the shore. Our dedicated DAC testing technology with our off-shore trained test engineers are vital in off-shore supporting customers with their after-installation testing, service life maintenance and cable asset management.

Regarding cable system tests, cable types, scope of tests, test procedures, criteria for evaluation of measurement results with e.g. mechanical-, electrical- and non-electrical tests such as:

Pre-qualification tests of the cable system consisting of: offshore- and onshore- cables, factory joint offshore joint, transition joint, land joint and cable terminations.
Cable system type and routine tests.
Inspection and acceptance tests (FAT).
Tests before laying the cable (verifying that the cable has not been damaged during loading onto a vessel or transport).
Inter-operational tests (connections subsequent cable sections, after other works).
Acceptance tests after building the cable line (SAT).
Maintenance test during cable line operation lifetime.
Test in case of a failure during operation.

Our expert team

Our expert team is able to support the process of determining the requirements for designing, installation testing and service life management of export- and inter-array cable systems.

Off-shore Inter-array Cables

There are mainly 2 options for testing the inter-array cables (IAC).

In the field of on and offshore power cable

Complete IAC string

One is to test a whole string with several WTGs connected. In that case it is preferred to setup the test equipment at the OSS and test the string from the OSS through the WTGs. To test the complete string the cable from the OSS is connected through the switchgear to the WTGs.

The complete cable will be tested through the switchgears of the individual WTGs. This has the benefit that the cable can be tested in the same configuration as under service conditions and it does not impair any risk to the switchgear. Furthermore, the test equipment can be setup on the OSS and multiple strings can be tested from the same location.

Complete IAC string

Individual IAC

Another option is to test the individual strings between each WTG separately. To test the individual strings between the individual WTGs, or from the OSS to the first WTG of that string. In this case the test equipment has to be setup at a WTG location. To reduce the number of mobilizations the selection the WTGs to be tested from has to be done in such a way that from each WTG the two strings can be tested (when possible).

Individual IAC

Off shore Export Cables

The off shore wind farm

Off-shore Export Cables

The off-shore wind farm (OWF) export cable circuits up to 275 kV are characterised by:

Due to circuits lengths up to 100 km high capacitance, which requires extremely high-power demand for conventional AC test systems.
Due to very long factory lengths large number of (factory) joints are installed.
There is a need to test the complete cable drum in the factory before shipping and on-site after installation.
Accessibility and space constraints regarding off-shore access to the cable.
No possibility for distributed partial discharge measurements on individual joints of a subsea cable.
In the case of HVAC or HVDC cables, any possible defects due to installation and transportation can only be detected and located with damped AC voltage testing including partial discharge detection.

Using DAC technologies, all these circumstances do not constitute any problem in the acceptance or diagnostic testing of export cables.