FIELD: electricity.
SUBSTANCE: invention is referred to relay protection and automatics of distributing electric networks, it may be used in municipal distributing cable networks. The essence of the invention consists in the selection of settings for current cut-off as the main protection for cable lines feeding two and more transformer substations (TS) with the sensitivity coefficient of 1.5 in the minimum mode of the feeding network, with the selected maximum current protection (MCP) as the reserve protection of TS 6(10)/0.4 kV and simultaneous entry of additional MCP stage as the reserve incombustible protection of the cable line matched in the actuation time with current cut-off (CCO) at input 6(10) kV of feeding substations, cable feeders outgoing from buses and simultaneous input of reclosing automatics (RA) operating in the dependence of the area short-circuit (ARA). At values of short-circuit currents more than minimum values of interphase short-circuit blocking (output) of RA operation is performed at the farthest end of the protected cable feeder of 6(10) kV.
EFFECT: minimised time for cut-off of the damaged cable line (feeder) at short-circuiting, as a result reduced destructive effect on insulation of factors related to short circuit currents, thermal (heating) and electrodynamic impact on the insulation of the feeder cables 6(10) kV at short-circuiting in the distributing cable network and reduced time of staying for personnel in dangerous areas of the operating electric installations due to the increased selectivity of protection equipment.
6 dwg, 2 tbl
