METHOD FOR PROTECTING A THREE-PHASED NETWORK FROM ONE-PHASED GROUND FAULT

摘要

FIELD: technology for protecting three-phased network with isolated neutral.;SUBSTANCE: in the method as electric value being controlled pulsing power of protected lines is used, which is selected by measurement or computation of instant power of three phases of the line and simultaneously its average value. Pulsing power of the line is determined by subtraction of average power from instant power. Measurements of computations of power components is performed continuously, before and after appearance of ground fault for all protecting lines. As input parameter for protection activation, increment of pulsing power is used, which is determined immediately after appearance of fault by subtraction of value of pulsing power, such as amplitude value, recorded before ground fault, from analogical current value of pulsing power. To measure or compute instant power of three phases of line and its components, phase voltages of network are used, which are measured relatively to the neutral of three-phased system, or linear voltages are used, which are phase-shifted in advance for minus 30° angle.;EFFECT: increased selectivity, increased reliability of protection.;4 dwg