Research On Reliability Of Zero-Sequence Protection Of Small Resistance Grounding In 10kV Distribution Network

The neutral ground working grounding modes of the 10 kV distribution network system: resonant grounding operation mode,ungrounded operation mode and small resistance grounding operation mode.Different grounding modes have different advantages and disadvantages.With the continuous expansion of the 10 kV distribution network system,its capacity and structure are constantly changing,resulting in more and more power supply companies starting to use small resistance grounding systems.In this paper,the principle and characteristics of three neutral point wiring modes of 10 kV distribution network system analyzes,and the steady-state and transient currents of zero-resistance grounding system and zero-sequence capacitor current distribution are obtaines;for the small resistance grounding system,the transition of the transition resistance and the metal-to-ground to ground fault builds;at the same time,it focuses on the analysis of the current transformer’s transmission error,selection principle and field application and gives the method of increasing the current transformer’s measurement accuracy;finally,the small resistance grounding system is analyzed based on the theory that multiple feeders and relative faults occur,and the relationship between the single feeder-to-ground fault and the zero-sequence current of multiple feeders and relative faults is obtained.And a new protection scheme is given,which will rely on the actual voltage of the busbar to dynamically change the zero-sequence current when the multiple feeders in the small-resistance grounding system and the relative grounding currents are the faults of a single feeder-to-ground fault.It ensures that when multiple feeders are in phase-to-phase fault,the protection settings of the primary equipment and the relay setting of the relay protection can still be applied,and the accuracy is not changed by the ground fault point and the fault type.