Protective method and device for distribution net work earthing fault

Abstract

This invention relates to a protection method for earth faults of distribution network including the following steps: 1, detecting if there is arc earth fault in three-phases of the network on-line, 2, if there is the fault in one phase, then its circuit is connected to the earth directly for a while, 3, on-line detecting if the fault happens to said phase, if so, said circuit is connected to the earth directly, otherwise returning to step 1, 4, repairing said circuit and returning to step 1. The device includes a single-chip control module, three voltage-inductors and three single-phase earth circuits, and the three voltage-mutual inductors are corresponding to one phase transmission circuit of the network.

Description

technical field [0001] The invention relates to a protection method and a device for a distribution network grounding fault. Background technique [0002] For a long time, most of the 3-35KV (including 66KV) power grids in my country have adopted the operation mode of ungrounded neutral point. When a single-phase grounding occurs in this type of power grid, the voltage of the non-fault phase to the ground will rise to the line voltage (UL), but the line voltage of the system remains unchanged. After a single-phase ground fault occurs, it is allowed to operate with faults for a short time. Therefore, the insulation level of various electrical equipment in this type of power grid, such as transformers, voltage / current transformers, circuit breakers, lines and other primary equipment, should meet the long-term requirements. The requirement to withstand line voltage without damage. [0003] The traditional concept holds that the 3-35KV (including 66KV) power grid belongs to th...

AI Technical Summary

Problems solved by technology

[0007] (2) When non-ground faults such as disconnection, non-full phase, and capacitive coupling of the same pole line occur in the power grid, the asymmetrical voltage of the power grid will increase, which may cause the automatic adjustment controller of the arc suppression coil to misjudge that the power grid is grounded and act , at this time, a very high neutral point displacement voltage will be generated in the grid, which will cause a large increase in the voltage of one or two phases in the system, which will damage other equipment in the grid

[0008] (3) The arc suppression coil has large volume, many components, high cost, large space for installation, and complicated operation and maintenance

[0009] (4) With the expansion of the power grid, the arc suppression coil must be replaced accordingly, which is not conducive to the long-term planning of the power grid

Due to the increased fault current, the arc grounding will aggravate the burning of the fault point

Images