Electricity: electrical systems and devices – Safety and protection of systems and devices – Automatic reclosing
Patent
1982-11-10
1985-05-07
Salce, Patrick R.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Automatic reclosing
361110, 361 94, 361 86, H02H 726
Patent
active
045161836
ABSTRACT:
An overcurrent relay comprises an input transformer (7), a rectifying circuit (8), a level detecting circuit (9) for providing an operation signal (S.sub.1) when a direct current signal voltage (E) exceeds a predetermined value, a determining means (10 to 15) for determining a time period of at least the positive and negative components of an ac signal voltage (V.sub.1) for providing a determination signal (S.sub.6) when the determined time period exceeds a predetermined time period, and a blocking means (16 and 17) responsive to the determination signal (S.sub.6) for blocking the operation signal (S.sub.1) from being output. In the case where the alternating current input current (I) and the ac signal voltage (V.sub.1) involve an attenuated direct current component due to magnetic saturation of a current transformer and the like, the reset time period of the operation signal (S.sub.1) is prolonged, while that time period of the ac signal voltage (V.sub.1) due to the attenuated direct current component becomes larger than a predetermined value, whereby a determination signal (S.sub. 6) is obtained. As a result, the blocking means (16 and 17) blocks the operation signal (S.sub.1) from being output, whereby a reset operation is performed. Therefore, the reset time period of the output signal (S.sub.7) is shortened.
REFERENCES:
patent: 3979645 (1976-09-01), Wittenzellner
patent: 4263635 (1981-04-01), Welk
Matsuzaki Tadashi
Sumi Koji
Mitsubishi Denki Kabushiki Kaishi
Salce Patrick R.
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