The judgment direction of cable repair in power engineering construction is as follows:
(1) Determine the nature of the fault. According to the phenomenon of the fault and some simple tests, we can preliminarily judge the nature of the fault, and determine whether the fault resistance is high resistance or low resistance, whether it is flashover or closed fault, whether it is grounding short circuit, broken line, or their mixture, whether it is single-phase, two-phase or three-phase fault. For example, when the cable in operation fails, if there is only grounding signal, it may be single-phase grounding fault; if the relay protection over-current trips, there may be two-phase or three-phase short circuit, or a mixed fault of short circuit and grounding. If the nature of the fault can not be determined by preliminary judgment, the insulation resistance must be measured and the conduction test must be carried out;
(2) Burn through of fault point. That is to say, high resistance fault or flashover fault can be changed into low resistance fault through burn through for rough measurement;
(3) Rough measurement. The instrument is used to measure the fault distance on one side of the cable, and the location of the fault point is calculated by using the technical data of the cable line;
(4) Path measurement. If the drawing data is not complete or the cable path is unknown, the laying path and buried depth of the faulty cable can be found out by audio induction detection method and pulse magnetic field method, so as to carry out fixed-point precise measurement. Audio induction detection method is to pass audio signal current into the wire, and determine the path according to the audio signal strength received by the receiver in the receiving coil.