To certainly easily detect and protect independent operations of non-utility power generating facilities in the course of system interconnection on the side of the non-utility power generating facilities, without providing expensive transfer interrupting device.
The output frequency and its change rate of the non-utility power generating facilities 8 to be linked with a system power source via a circuit-breaker are detected, and a voltage variation reference for increasing the leading reactive power of the generating facilities 8, when the change rate of the frequency is positive, or increasing the lagging reactive power when the change rate is negative, is outputted. Also a frequency variation which is fostered by voltage variation of the generating facilities 8 produced by adding a compensated voltage variation reference obtained by compensating the voltage variation reference, in order to compensate for the influence given to rotational speed variation by an inertia constant in the rotational speed control system of the generating facilities 8, to a voltage reference of an automatic voltage regulator 12 of the generating facilities 8, is detected, circuit-breaker is opened, and parallel off of the generating facilities 8 from system bus-bars is made to be executed.
KATO TOYOKUNI
TOCHIO SHINICHIRO
NISHISHIBA DENKI KK
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