Non-grounding neutral point system low-voltage leakage protection method and its equipment

Abstract

The method and equipment is in use for system of its neutral point not connected to ground under well of coal mine. Using centralized control mode, the method centralizes zero sequence current (ZSC) of each branch switch to a device. The device controls each branch switch and main switch. Comparing with prior art, the invention eliminates not unitive criteria for electric leakage of each branch switch and main switch; eliminates unwanted operation factors from influence of change of system voltage and system capacitance on corresponsive zero sequence voltage (ZSV) of leakage resistance. Integrated applying three types of algorithm including method of abrupt change quantity of ZSC, phase method of ZSC and ZSV, and relative phase comparison method of ZSC, the invention selects one of the algorithms automatically based on relative merits and physical circumstances of system. When leakage occurred at multiple branches, the invention trips off the branch with largest leakage current.

Description

Technical field [0001] The invention relates to the field of leakage protection, in particular to a low-voltage leakage protection method and equipment for an underground neutral point ungrounded system in a coal mine. Background technique [0002] In underground coal mines, low-voltage 380V, 660V and 1140V voltages are neutral point ungrounded systems, and leakage is the most common fault. [0003] The two indicators to measure the leakage are the leakage resistance value and the operating time. Since the leakage resistance value is affected by many factors, and the operating time is required to be very short (within 30ms), the original technology fails to really solve the problem of low-voltage leakage protection. [0004] The original low-voltage leakage protection equipment adopts a decentralized control mode: the leakage detection relay for detecting bus leakage is a single explosion-proof device, and the protection unit for detecting branch circuit leakage is installe...

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Problems solved by technology

Second level protection delay 250ms

This is the reason why it is easy to misjudgment the short branch without leakage (the capacitance current of the short branch without leakage is very small) when using the principle of "zero-sequence current and zero-sequence voltage phase method".

[0013] 4. Unable to solve the problem of distributed leakage

[0014] 5. Intelligent low-voltage switches still cannot solve the problem of leakage protection: in some low-voltage switches controlled by single-chip microcomputers, both the bus and branch feed switches have leakage protection functions, and their control principles are the same as the "leak detection relay" mentioned above. , "protection unit" principle is exactly the same

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