EA Technology has launched what it says is the world's first combined ultrasonic and transient earth voltage (TEV) hand-held instrument, capable of detecting both surface and internal discharges in electricity switchgear. Called UltraTEV, it combines ultrasonic sensors to pick up early signs of surface discharge, with TEV sensors to detect internal discharges. The company expects it rapidly to become standard equipment for field engineers.
A significant proportion of switchgear in-service failures is caused by insulation breakdown, usually signalled by increasing levels of partial discharge activity. Early detection of these discharges can prevent catastrophic failure
The instrument features two indicator lights, for ultrasonic activity and TEV activity. The TEV indicator shows green for 'OK', amber for 'warrants checking more frequently’, and red for 'requires immediate investigation using more sophisticated instruments'.
The key to the UltraTEV's accuracy is the threshold levels to which the condition indicators have been set. These have been derived from measurements of partial discharge taken in 6000 substations and involving nearly 50 000 switches. They are stored in a database built up by EA over 37 years.
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