The electrical distribution system on the Isle of Man is linked to the UK power system via a 90kV AC subsea interconnector cable. The total length of the interconnector is approximately 108 km of which about 104 km is subsea cable.

This is a key installation for the Manx Electricity Authority and ERA has recently provided assistance with a strategy to deal with any fault on the interconnector. In the event of a fault, one of the first requirements is to obtain a reliable estimate of where the actual problem is located along the cable. This is not easy as most fault location equipment cannot provide accurate information for such a long length of cable.

t 108km route of the Manx AC Interconnector Comparison of EMTP model (right top) and TDR measurements on cable (right bottom) u

To solve the problem, ERA used an electromagnetic transients programme (EMTP) to build a theoretical model to predict the magnitude of the TDR (time domain reflectometer) pulse likely to be effective over the whole length of the cable. The model was then verified by field trials of high power TDR measurements. ERA's cable engineers were able to locate the remote end of the interconnector and a known subsea joint at about 60km from the test point. The joint was located to within 150m of the position determined from the installation records, a location accuracy of 99.86% across the total cable length.

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About ERA Technology
ERA Technology works at the leading edge of many advanced technologies. The business was founded in 1920 and today provides specialist, high value-added, technology-based services including design and development, testing, assessment and expert advice.

The company has built an international reputation for technical expertise through constant innovation at the leading edge of technology. ERA's services reduce technical and commercial risk, improve the operational performance of engineering infrastructure assets, and enhance the competitiveness of products and systems.

ERA Technology is a Cobham company.