IEVref:448-15-15ID:
Language:enStatus: Standard
Term: unblocking overreach protection
Synonym1: UOP (abbreviation)
[Preferred]
Synonym2: unblocking directional comparison protection (US)
[Preferred]
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Definition: protection, generally distance protection, using telecommunication, with overreach protection at each section end and in which a blocking signal is transmitted continuously to the other section end until a fault is detected by the overreach protection which removes the blocking signal and sends an unblocking signal to the other end. Removal of the blocking signal together with the receipt of the unblocking signal permits the initiation of tripping by the local protection

NOTE – If no unblocking signal is received following removal of the blocking signal, it is usually arranged to permit the overreach protection to initiate tripping within a variable time interval usually in the range 100-200 ms.

See figure 448-9.

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Publication date:1995-12
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Internal notes:2012-12-18: Corrected for conformity with standard: terms and synonyms correctly structured; source content transferred to definition field. JGO
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