In a three-phase power system, only one phase of the insulation between the conductor and the ground is broken.
Broadly speaking, single-phase grounding faults include single-phase grounding short-circuits. Single-phase grounding short-circuits are a special phenomenon in single-phase grounding faults, which can only be found in transformer neutral grounding systems.
In a narrow sense, single-phase grounding fault and single-phase grounding short-circuit are two concepts. One is a malfunction, the other is an accident.
Power system faults and accidents are distinguished in a narrow sense.
Single-phase grounding short circuit means that the live wire (any phase of electricity) is directly connected to the ground wire without passing through the load. In the 380/220 power supply system or other grounding systems, the neutral wire of the transformer is grounded and the ground resistance is very small. , The live wire (any phase of electricity) is directly connected to the ground wire without passing through the load, and a large current will be generated instantly, burning wires, power distribution equipment or tripping, etc., so a single-phase grounding short circuit is a serious accident, which is electricity. The system should be avoided as much as possible.
In the power system, there are many places that use ungrounded systems for power supply. For example, in special places such as severe dust, inflammable and explosive, all 6-10 kV, 35 kV power supply systems in our country, etc., use neutral A power supply system that is not grounded or grounded through a large resistance. After such a system is single-phase grounded, since there is no loop or loop that generates a large current, there is no ground current or large ground current, so it does not affect the normal operation of the system. Although it does not affect the normal operation of the system, single-phase grounding is a fault. In order to prevent grounding from expanding to two-phase grounding or further damage to grounding equipment, the regulations stipulate that after a single-phase grounding fault occurs, it must be checked within 2 hours. If the cause cannot be found or cannot be handled within 2 hours, the power can be supplied only after the power failure is dealt with.