Earthing compensation process for mine low-voltage electricity grid selective leakage protection system

Abstract

The invention relates to an earth compensation method of a mine low temperature electrified wire netting leakage protecting system, which is characterized in that each adjacent branch switch of the mine low temperature electrified wire netting leakage protecting system fixes a choosing leakage protector, a zero-sequence reactance LK and a three-phase reactance SK, wherein it uses each branch zero-sequence reactance LK to generate electric inductance current IL to compensate the local wire earth capacity current Ic. It adopts the out branch scattering compensation mode to displace the traditional power bus concentrating compensation mode.

Description

1. Technical field: [0001] The invention belongs to a selective leakage protection system for mine low-voltage power grids. 2. Technical background: [0002] Underground low-voltage power grids in my country's coal mines are generally neutral point ungrounded systems. When a single-phase earth leakage occurs in this system, a capacitive arc current of tens to hundreds of milliamperes will be generated at the grounding point, resulting in personal electric shock or gas explosion. For this reason, in this system, the neutral point of the three-phase reactor SK is connected to a zero-sequence reactor LK and then grounded through the capacitor C, and the inductive current I can be generated. L It is used to compensate the grid-to-ground capacitance current I C , thereby reducing unsafe factors. [0003] However, the existing low-voltage leakage protection devices in my country (such as widely used KXL-1, BJJ type and leakage selection devices in various comprehensive protecti...

AI Technical Summary

Problems solved by technology

[0003] However, the existing low-voltage leakage protection devices in my country (such as widely used KXL-1, BJJ type and leakage selection devices in various comprehensive protection devices, etc.) all adopt the principle of zero-sequence power direction or phase-sensitive protection. Therefore, they can only be applied to the underground low-voltage power grid without zero-sequence reactor compensation function, otherwise the system will enter the "dead zone" due to possible grounding overcompensation, and lose the protection function of leakage selection

Therefore, in order to ensure the "horizontal selectivity" of leakage protection, the existing underground low-voltage leakage protection systems are all "systems without grounding compensation", that is, such leakage protection systems do not have the ability to compensate the ground capacitance current of the low-voltage power grid. function, the only zero-sequence reactor in the general leak detection relay of the low-voltage power grid is abolished (or directly replaced by a resistor, or an equivalent capacitor is connected in parallel next to the zero-sequence reactor), which obviously increases the personal electric shock It also increases the possibility of ground fault current detonating gas, which is obviously not good for coal mine safety, and does not meet the express provisions of Article 4.2.4 and Article 5.14 of JB6314-92

Images