Protection system mal-operations result from a failure, a malfunction, or an unanticipated or unplanned operation of the protective system. This can cause either incorrect isolation of a no-trouble area, or a failure to isolate a trouble area.
The reasons for incorrect operation can be one or a combination of
(1) misapplication of relays,
(2) incorrect setting,
(3) personnel errors, and
(4) equipment problems or failures (relays, breakers, CTs, VTs, station battery, wiring, pilot channel, auxiliaries, and so on).
It is practically impossible to anticipate and provide protection for the numerous possible power system problems. With the best of planning and design there will always be a potential situation that may not be ‘‘protected,’’ or an error not detected. Occasionally, these are ‘‘covered’’ by an incorrect operation that can be classified as ‘‘acceptable for the particular situation.’’ Although these are very few, they have saved power systems and minimized embarrassments.
Principles and Applications
J. Lewis Blackburn
Thomas J. Domin