METHOD OF FAST-ACTION REMOTE PROTECTION OF D C OR A C POWER LINE BY INSTANTANEOUS CURRENTS AND VOLTAGES Russian patent published in 1995 - IPC

FIELD: relay protection. SUBSTANCE: in compliance with method previously unknown regularity of distribution of predicted voltage along power line is used. Voltage is predicted with assumption that line is not faulty independent of its real state. If there is fault then predicted voltage changes its sign with passing through point of short-circuit. In agreement with given method all phase and line voltages are predicted at the end of protected zone. Their signs are compared with signsof corresponding measured voltages. Oppositon of signs is sufficient for operation of protection of direct voltage power lines. But for alternating voltage power lines there are required additional parameters, for instance, increments of measured and predicted voltages. Protection operates if increment signs are also opposite as well as signs of voltages proper. EFFECT: improved reliability and efficiency of protection. 4 cl, 6 dwg