Detect and locate power cable faults

After experiencing a short circuit, locating the fault is normally a manual, time consuming process that delays repairs—leaving assets offline and idle. The OptaSense Integrated Smart Sensing system monitors for ground strain, temperature changes and shock waves in order to detect and locate short circuits in real-time, with +/- 10m accuracy.

Rapid and Accurate Short Circuit Detection

While operating on an offshore windfarm in Scotland, midway between the Galloway and Cumbrian coasts, our client experienced a short circuit on a main export cable approximately 15km in length, of which 13km was located subsea. Until the fault could be located and repaired, 80MW of offshore power would be sitting idle.

Existing Time Domain Reflectometry (TDR) methods using a high voltage pulse generator indicated the fault was 2km offshore. A repair in this location would cost the operator £8M, in addition to placing the wind turbines offline for up to 6 months—accruing a potential loss of revenue of £90,000 per day. Locating a fault using the TDR technique is a lengthy process with a lower location accuracy of +/- 300m on a 15km cable.

As with many export and inter-array subsea power cables, the export cable had an existing fiber optic cable integrated within the structure—meaning the rapid deployment of DAS was possible. OptaSense experts mobilized quickly, arriving onsite within 24 hours and locating the fault within 4 hours of arrival.

The location of the discharge noise, which was caused by the generator, was determined in minutes. OptaSense verified that the fault was actually located onshore, eliminating up to eight weeks of offshore repair time at £10K per day and lost revenue for the operator. By determining that the fault was onshore we eliminated the additional need and high cost for vessels and ROV’s.

How Power Line Failure Detection Works

When a short circuit occurs it generates an acoustic signature that can be detected in real time by the OptaSense Integrated Smart Sensing system.

During a short circuit, energy physically flows into the surrounding earth, resulting in ground heave, which places strain on the fiber. Our system detects this strain to locate faults within 5m to 10m of the occurrence on subsea cables, underground cables or cable tunnels. The system also identifies changes in temperature caused by the impact of transient strain at the time of an electrical power surge.

To further pinpoint a fault location, the system detects shock wave ripples, or negative pressure pulses, caused by the transient power dissipation that propagates both upstream and downstream from the short circuit location.

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