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    • 9. 发明专利
    • DETECTING RELAY FOR UNDERVOLTAGE CHANGE AMOUNT
    • JPH06141459A
    • 1994-05-20
    • JP28600392
    • 1992-10-23
    • TOSHIBA CORP
    • SAITO HIROSHI
    • G01R19/12H02H3/44
    • PURPOSE:To detect an accident at high speed and with high sensitivity by detecting an undervoltage change amount generated in the accident caused in an electric power system. CONSTITUTION:By using a sampling value which has sampled an introduction voltage from an electric power system at a definite cycle and which has been converted into a digital amount from an analog amount, the difference value DELTAm between a present-voltage sampling value Vm and a voltage sampling value Vm-n prior to the definite cycle is computed. Then, the inner product value ¦DELTAV¦.¦V¦costheta' (=DELTAVm.Vm+DELTAVm-n.Vm-k) of the present-voltage sampling value Vm and the difference value DELTAm is computed, and the magnitude of a set value K, which has been set in advance compared with the magnitude of the inner product value¦DELTAV¦.¦V¦costheta'. When the inner product value ¦DELTAV¦.¦V¦costheta'>=K1 (where K1 is the set value), it is judged that an accident has been caused in the electric power system, and an operation is output. Thereby, the accident of the electric power system can be detected at high speed and with high sensitivity.