This paper introduces several methods to find the fault of leakage protector for reference.
1、 Patrol inspection method
The patrol inspection method is a method for the responsible (on duty) electrician or staff to check all leakage protection systems (including all leakage protectors and the protected power grid) to find faults according to the analysis and judgment of the fault phenomenon. It mainly depends on human eyes to find fault points, so it is simple and easy to operate, especially suitable for fault finding with obvious fault points. For example, the conductor falls off the ground, trees touch the conductor, the guy wire contacts the conductor, the leakage protector is burnt out, and various wrong installation and wiring.
2、 Instrument test method
The instrument test method is a method to test some parameters of the power grid or equipment with the help of the functions of the instrument, and judge the cause of the fault or directly detect the fault point. For example, the perimeter of the motor or household electrical equipment is grounded by touching the shell, the power grid insulation is damaged, the leakage current and the change of the unbalanced leakage current can only be found through the test of the instrument.
3、 Commissioning method
When a leakage protector has an action tripping fault, and no obvious fault is found through patrol inspection or instrument test, the leakage protector and the protected grid can be put into operation for a trial power transmission. If the trial operation is successful, it indicates that the previous fault has disappeared, and the action tripping may be caused by transient fault. For example, it may be caused by electric shock in the protected power grid, wind swaying tree touching the conductor, transient over-voltage, overload of the power grid, large motor starting, or strong magnetic field, strong vibration, etc. The trial operation method is to put the tripped leakage protector and the protected power grid into operation again, so as to re judge whether the previous fault is transient or permanent, and if it is permanent Then other methods must be used to find the fault point, if it is a transient fault (the fault point has disappeared). Power transmission operation can be resumed. The trial operation method is the most simple and convenient method. Especially for the leakage protector tripping caused by various transient faults, the trial operation can be successful once, which greatly reduces the outage time and improves the reliability of users' power consumption.
4、 Graded or segmented selection method
In case of leakage or grounding fault in the protected power grid that causes the leakage protector to permanently act and trip, each branch line of the low-voltage power grid can be disconnected first in the order of "main network branch terminal", and then only the main line is tested for power supply and the leakage protector is put into operation at the same time; Or first pull off the section switches of the low-voltage power grid, and then only test power supply to the power side and the first section of the power grid, and simultaneously put in the leakage protector. If there is no fault in each trunk line or the first section of power grid, the leakage protector can be put into operation normally. Then switch on the branch line in turn or turn on the next section switch.
5、 Simulated jumping method
The simulated tripping method is a method specially used to check whether the leakage protector in operation has the failure of rejecting action. The leakage protector will sometimes refuse to act during operation. In order to prevent personal electric shock casualties caused by the failure of the leakage protector to act, the leakage protector itself and the protected power grid should be regularly subject to simulated leakage action tests. We call this method to check whether the leakage protector itself or the protected power grid has the failure of rejecting action the simulated tripping method. The simulated tripping method includes the tripping test of the leakage protector itself (i.e. "internal test") and the simulated leakage action test of the protected power grid (i.e. "external test").
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