New Maintenance and Testing Strategies for Protection and Control
The electric utility industry has a history of thorough testing of protective relays. This has been driven by the fact that, for most of the 20th Century, relays were silent observers of the power apparatus they protected, reacting only to faults and abnormalities. Electromechanical and solid state analog relay designs could fail or drift out of calibration without any indication, leading to failures to trip or false trips later.
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