A single-phase high-resistance grounding fault detection method in a small-resistance grounding system
A high-resistance grounding fault and low-resistance grounding technology, applied in the fault location, detecting faults by conductor type, measuring electricity, etc. Acquisition and processing, easy-to-engineer effects
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Embodiment 1
[0044] A method for detecting a single-phase high-resistance ground fault in a small-resistance grounding system. The implementation of the feeder zero-sequence protection adopted in this embodiment is as follows:
[0045] S1. Assign the initial value to the zero-sequence voltage mutation start value U 0.set , The minimum value of instantaneous reactive power Q min , protection action setting value Z set and action duration setting value T last ;
[0046] Among them, U 0.set The value of U needs to consider the size of the zero-sequence voltage when the high-impedance ground is connected, as well as the sampling frequency, U 0.set The smaller the value, the more sensitive the algorithm is; Q min The value of Z needs to consider the stability of the algorithm, and its value cannot be too high, otherwise the protection will refuse to move; Z set The value of T needs to consider the actual small grounding resistance and the zero-sequence impedance of the zigzag transformer,...
Embodiment 2
[0065] Take a substation with a 10kV neutral point as a small resistance grounding method as a model. The resistance of the small grounding resistor is 10Ω, the zero-sequence impedance of the zigzag transformer is 10Ω, and the lengths of feeder lines 1, 2, 3, and 4 are 6km, 9km, 12km, and 15km respectively. Each feeder line adopts cable lines, and the model is YJV 22 -3*300, the positive sequence parameters are: R1=0.500Ω / km, L1=0.318mH / km, C1=0.376μF / km, the zero sequence parameters are: R0=0.500Ω / km, L0=6.398mH / km , C0=0.370μF / km. The load rate of the distribution transformer is 60%, and the power factor is cosθ=0.9.
[0066] In this embodiment, a single-phase ground fault is installed at the end of the feeder 3 with a length of 12 km. The fault types are linear transition resistance fault and arc fault respectively, and the fault time is when the voltage of the fault point to ground reaches its peak value. The effectiveness of the present invention is verified by taking t...
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