Abstract: A control system for canceling load unbalance of a three-phase circuit includes phase current detectors for detecting phase currents caused to flow through a secondary circuit of a current transformer provided in high voltage distribution lines, respectively, phase change-over switches through which phases of the high voltage distribution lines, and primary sides of distribution transformers provided across high and low voltage distribution lines are connected to each other, a control center for, when a magnitude of a zero-phase current detected by the zero-phase current detector is larger than a predetermined value, on the basis of the phase currents, respectively, out putting a control signal so that the load of the phase having a maximum current appearing therein is changed over to the phase having a minimum current recognized therein, and a phase change-over slave station for controlling the phase change-over for the phase change-over switches in accordance with the control signal.

Abstract: A monitoring and control system includes a center main system (209) installed in a sales office and a substitute center system (208). The monitoring and control system further includes a different substation terminal interconnection function that, in the case where there occurs an abnormality to a communication channel provided for each substation terminal and connects the substation terminal to the center main system (or the substitute center system), instructs a different substation terminal to perform the interconnection and communication with the center main system (or the substitute center system) instead of the substation terminal. With this construction, through the different substation terminal that received the instruction, the center main system monitors and controls a switch to be monitored by the substation terminal connected to the communication channel to which the abnormality occurs.

Abstract: A ground relay system is provided which includes: first current transformers located in the respective phases of a sending end of a high-voltage distribution provided from a distribution substation; over-current relays connected to the first transformers; distribution transformers located in the respective phases in the respective sections of the distribution; second current transformers connected to secondary sides of the distribution transformers; current converters connected to the second transformers; and a current comparator that introduces the currents of the respective phases of the sending end of the distribution from the relays to produce a first zero-phase current, introduces the currents of the respective phases of a load end of the high-voltage distribution from the current converters to produce a second zero-phase current, and operates a ground protection relay that opens a circuit breaker inserted at the sending end of the high-voltage distribution if the level of the first current is larger.

Abstract: A control system for canceling load unbalance of a three-phase circuit includes phase current detectors for detecting phase currents caused to flow through a secondary circuit of a current transformer provided in high voltage distribution lines, respectively, phase change-over switches through which phases of the high voltage distribution lines, and primary sides of distribution transformers provided across high and low voltage distribution lines are connected to each other, a control center for, when a magnitude of a zero-phase current detected by the zero-phase current detector is larger than a predetermined value, on the basis of the phase currents, respectively, out putting a control signal so that the load of the phase having a maximum current appearing therein is changed over to the phase having a minimum current recognized therein, and a phase change-over slave station for controlling the phase change-over for the phase change-over switches in accordance with the control signal.

Abstract: A monitoring and control system includes a center main system (209) installed in a sales office and a substitute center system (208). The monitoring and control system further includes a different substation terminal interconnection function that, in the case where there occurs an abnormality to a communication channel provided for each substation terminal and connects the substation terminal to the center main system (or the substitute center system), instructs a different substation terminal to perform the interconnection and communication with the center main system (or the substitute center system) instead of the substation terminal. With this construction, through the different substation terminal that received the instruction, the center main system monitors and controls a switch to be monitored by the substation terminal connected to the communication channel to which the abnormality occurs.

Abstract: A ground relay system is provided which includes: first current transformers located in the respective phases of a sending end of a high-voltage distribution provided from a distribution substation; over-current relays connected to the first transformers; distribution transformers located in the respective phases in the respective sections of the distribution; second current transformers connected to secondary sides of the distribution transformers; current converters connected to the second transformers; and a current comparator that introduces the currents of the respective phases of the sending end of the distribution from the relays to produce a first zero-phase current, introduces the currents of the respective phases of a load end of the high-voltage distribution from the current converters to produce a second zero-phase current, and operates a ground protection relay that opens a circuit breaker inserted at the sending end of the high-voltage distribution if the level of the first current is larger.

Abstract: A distribution control system that can isolate a fault section without fail, even if control of load break switches becomes impossible because of a communication error between a control center and a feeder terminal unit. If a communication error takes place between the control center and a particular feeder terminal unit, for example, feeder terminal units associated with the particular feeder terminal unit change the operation mode of their controlling load break switches from non-voltage unopened mode to non-voltage open mode.