FIELD: electrical and power engineering; locating faults in three-phase overhead insulated-neutral lines. SUBSTANCE: method is used for locating defective line at the same time determining distance to single-phase ground fault in 6- to 35-kV three-phase overhead insulated- neutral lines followed by their disconnection. For locating defective line and its ground fault zero-sequence current flowing during preceding mode through each line is stored, change in zero-sequence current through each line during commercial-frequency period is determined and compared with respective setting for each line; if current at one of junctions has not reversed during commercial-frequency period and is higher than setting value, conclusion is made that line is defective and this line is disconnected; point of ground fault is determined using formula 
, where Igfl is emergency zero-sequence current of defective line; ΣInl is total zero-sequence current of normal line; Ip-a is pre-accident zero-sequence current of defective line; Igf2,...,Igfn is capacitive current of substation lines 2 through n; C0 is specific capacitance of line; U is mains voltage; l1.1 is length of defective line between substation and ground-fault point; l1.2 is length of defective line between point of ground fault and end of line. EFFECT: reduced time of ground-fault location including simultaneous determination of distance to ground fault and line disconnection. 2 dwg
