Patent ID: 7579712
Filing Date: 2009-08-25
Classification: H02J,Y02E

Abstract:
1. A power system protection system for stably operating a power system, comprising: a main device for acquiring a system electric quantity of one or a plurality of upper substations of said power system; and a terminal device for acquiring a system electric quantity of one or a plurality of lower substations that receives power from said upper substation and supplies power to loads, wherein: said main device includes: a system voltage gradual drop determination unit that outputs a system voltage gradual drop determination signal when the voltage drop rate in a long time region exceeds a predetermined value based on a three-phase voltage of the power system and terminates the outputting of said system voltage gradual drop determination signal when the three-phase voltage of the power system exceeds a voltage recovery set value; a system voltage sudden drop determination unit that outputs a system voltage sudden drop determination signal when the voltage drop rate in a short time region exceeds a predetermined value based on a three-phase voltage of the power system and terminates the outputting of said system voltage sudden drop determination signal when the three-phase voltage of the power system exceeds the voltage recovery set value; an operation-prioritized selection unit that outputs an operation-prioritized selection signal early when the voltage drop in the three-phase voltage of the power system is large and outputs the operation-prioritized selection signal late when the voltage drop is small; and an output permission unit that outputs an output permission signal in the event of the voltage sudden drop resulting from a reactive power characteristic, and wherein said terminal device includes: a load shedding output unit that sequentially sheds loads starting from those of the lower substations suffering more from the influence of the voltage drop resulting from the reactive power characteristic when receiving the system voltage gradual drop determination signal and the operation-prioritized selection signal from said main device; and a load shedding selection output unit that selects loads causing the voltage sudden drop resulting from the reactive power characteristic and sequentially sheds the selected loads when receiving said system voltage sudden drop determination signal and said output permission signal from said main device.