Classification Of Short Circuit And Ground Fault Detection Methods

       There are various types of cable fault, and effective detection methods can make cable fault detection more convenient. Next, GDZX will give a brief introduction about the detection methods of cable short circuit and grounding fault.

I Judgment basis of short circuit fault

1. Over current mutation method of adaptive load current. In order to improve the accuracy, it is necessary to determine a time width of sudden change current with the relay protection device of substation.

2. Quick break method. When the short-circuit fault occurs in the cable line, the outlet protection of the substation line will act, the line will be cut off after the switch trips, and the current in the line will be zero.

3. Over current method. When there is a short circuit fault in the line, the current value passing through the wire will increase suddenly. The current value is related to the cable length, model, laying mode, environmental temperature and other factors.

II Ground fault judgment basis

1. Detect the magnitude and direction of zero sequence fundamental wave. The line structure is complex and unreliable with arc suppression coil, which can be compensated by on-line monitoring and parameter adjustment. Digital fault indicator LPK2-E detects the magnitude of zero sequence fundamental wave

2. Detect the magnitude and direction of the fifth harmonic of zero sequence. It can not be switched on when there is voltage fluctuation and nonlinear load.

3. Zero sequence transient analysis method. It can be compensated by on-line detection and parameter adjustment.

4. Hand half wave method. Hand half wave method is unreliable when the direction of grounding current and load fluctuate greatly, which can be compensated by on-line detection and parameter adjustment.

5. Transient analysis method of stray capacitor instantaneous discharge. Transient peak current direction and load fluctuation are unreliable, which can be compensated by on-line detection and parameter adjustment.

6. Low resistance grounding method. When the neutral grounding mode is changed, the zero sequence two-stage protection is used to detect the ground fault.

7. Medium resistance intelligent grounding, a signal source method. Through the switch sequence control, the neutral point is intermittently grounded regularly through the middle resistance, so as to realize the grounding signal and repeat the grounding process.

8. High voltage pulse / low frequency current method, a signal source method. Firstly, the power is cut off, and the fault phase line is discharged by high-voltage capacitor, or DC component current is continuously applied, and then a low-frequency component current is added.

9. Manual or automatic closing trial power transmission method.

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