Protective relay

Details Protective relay Protective relay

1984-01-23

1985-12-31

Salce, Patrick R.

Electricity: electrical systems and devices

Safety and protection of systems and devices

With specific quantity comparison means

361 82, 361 84, 361 67, H02H 326

Patent

active

045625077

ABSTRACT:
A protective relay which hardly makes maloperation in itself regardless of mixing of low-order higher harmonics in its at least two sinusoidal input signals comprises a first and a second phase detection comparator generating two different-phase square signals indicative of the phase difference between the sinusoidal input signals, a first and a second timer receiving the square signals generated from the first and second phase detection comparators respectively and generating their output signals as a result of comparison between a first period of time and one of the periods or the period of presence or absence of the square signals, a third timer receiving the same square signal as that applied to the first timer and generating its output signal as a result of comparison between a second period of time and the other period or the period of absence or presence of the square signal, a fourth timer receiving the same square signal as that applied to the second timer and generating its output signal as a result of comparison between the second period of time and the other period or the period of absence or presence of the square signal, a first flip-flop set by the first timer and reset by the third timer, a second flip-flop set by the second timer and reset by the fourth timer, and a third flip-flop set and reset by an AND circuit and a NOR circuit respectively connected to the outputs of the first and second flip-flop.

REFERENCES:
patent: 3379934 (1968-04-01), Hoel et al.
patent: 3832601 (1974-08-01), Hinman, Jr. et al.
patent: 3890544 (1975-06-01), Chamia
patent: 4447845 (1984-05-01), Wilkinson

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