Time-saving HV tester fits in a suitcase

A technique for testing high-voltage motors, switchgear and transformers in a matter of minutes, without having to shut down the equipment, has been developed by three British companies. Traditional techniques for detecting partial discharges in HV equipment - such as dielectric loss analysis - can take up to 12 hours and require the system to be shut down, before it is stressed up to the operating voltage.

The new technique, developed jointly by HV Solutions, M&B Systems (Power Instrumentation), and Wyko Condition Monitoring, uses a set of small coils and a suitcase-sized detector, rather than the van-full of equipment needed previously.

The developers worked closely with Professor David Edwards who first realised that a device known as a Rogowski coil, originally used to detect high-frequency radio waves, could also be used to monitor partial discharges in HV circuits. Once fitted to the HV equipment, the Rogowski coils stay there and are simply plugged into the detector, which can then provide detailed analyses of the equipment`s health in a non-invasive way.

The detector can also accept inputs from other sources, such as capacitative couplers, radio frequency current transformers, transient earth voltage probes and acoustic devices. It can analyse the information from the various sources to provide a more accurate and comprehensive picture of the system`s health, as well as predicting its future behaviour.

According to Ian Smith, Wyko`s technical development manager, the equipment will allow personnel to detect problems such as surface contamination, internal and inter-phase discharges, surface tracking, and end-winding and slot section movements.

"By using one piece of test gear, as opposed to the mini container-load of heavy, cumbersome equipment traditionally required," he says, "Wyko engineers can asses larger plants and installations in a fraction of the time".