LOAD UNBALANCE RESOLUTION CONTROL SYSTEM FOR THREE-PHASE CIRCUIT

摘要

PPROBLEM TO BE SOLVED: To resolve the problem of a conventional system that an overcurrent ground relay (OCGR) malfunctions due to an unbalance of load. PSOLUTION: This system is provided with a phase current detector 73 which detects a phase current flowing through the secondary circuit of a current transformer provided in a high-voltage distribution line, a zero-phase current detector 75 which detects a zero-phase current flowing through the residual circuit of the above current transformer, phase changeover switches 141-1410 for connecting with each phase of the above high-voltage distribution line and the primary side of a distributing transformer provided between a high-voltage line and a low-voltage line, a control center 11 which outputs a control signal so that it may switch the load of a phase where a maximum current has appeared into a phase where a minimum current is perceived, based on the phase current of each phase detected by the above phase current detector, in case that the above detected zero-phase current is larger than a specified value, and phase switching substations 131-1310 which control the phase switching of the above phase changeover switches, based on the above control signal. This can eliminate the unbalance of a three-phase circuit and can prevent the malfunction of the overcurrent ground relay. PCOPYRIGHT: (C)2005,JPO&NCIPI