In the operation of small current grounding network, when single-phase grounding fault occurs, when the ground signal is reported by the cut-off level monitoring, the operation personnel on duty should deal with it calmly. According to the signal, voltmeter indication, weather conditions, operation mode and so on comprehensive analysis, distinguish the ground signal virtual and real. And timely report to the superior dispatch and leadership, do a good record of the phenomenon.
In the judgment processing, the fault nature and phase should be identified according to the characteristics of the grounding fault. Secondly, sub-network operation is carried out to reduce the scope of power failure. Power balance between various parts and relay protection coordination should be considered when sub-network operation. And then check the electrical equipment has no fault: such as equipment porcelain part is not damaged, there is no lightning flashover; There are no falling objects, small animals and external damage phenomenon on the equipment; Grounded with or without broken wires. Then check whether the fuse of the transformer is broken, whether the lightning arrester and cable end are broken down and damaged, etc. On the premise of confirming that there is no problem in the equipment, use the instantaneous stop and pull the brake in turn to find the method.
At present, some 10kV outgoing line of 35kV substation is equipped with grounding signal device or microcomputer line selection device. When the device is put into operation normally, it is easy to distinguish and find out the grounding fault line. If the outgoing line is not equipped with grounding signal device, the search and treatment method is: disconnect the branch switch of 10kV line bus in turn. If the grounding signal of the disconnect switch disappears and the indication of the insulation monitoring voltmeter returns to normal, that is, the power failure line has grounding fault, and the fault can be arranged to eliminate.
If the grounding signal still exists after the transient stop shunt switch, it means that the grounding fault does not occur in this line, the power supply should be restored immediately, and then other lines should be stopped according to the transient, do not disconnect all outgoing lines for search. So will all the 10 kv line open and disconnect, is to remove all the qualification of capacitive current, this will cause the system capacitive current slash, residual current is too large, lead to lose arc suppression coil of arc extinction effect, which is on the site to produce intermittent arc discharge, shaw trigger overvoltage, the threat to equipment insulation. Therefore, when using the transient stop search method, do not completely disconnect the line and search, but stop one way to check one way, and then stop the other way after the power supply is restored.
After the grounding fault is found, the user line that is not important in general can be cut off to troubleshoot the grounding fault. After the grounding fault is rectified, the power supply can be restored.
If the power supply line of an important user is grounded, measures should be taken to transfer the power load, or put into the standby line. After these works are done, the grounding fault can be found and eliminated before the power failure, and the power supply can be recovered as soon as possible to reduce the loss of power failure.
Wuhan Xinshengneng Technology Co., LTD
