A DC grounding alarm based on open current detector

Abstract

The invention discloses an opening current detector-based direct current grounding alarm, which comprises opening current detectors, an acousto-optic alarm circuit and a signal detection processing module, wherein the opening current detector is arranged at a load side of each branch of a direct current secondary loop to be detected, each opening current detector comprises an annular iron core and a coil wound on the annular iron core, the annular iron core is formed by detachably assembling two half-annular iron cores, a first clearance and a second clearance are formed between end surfaces of the two half-annular iron cores, the width of the first clearance is greater than the width of the second clearance, and a magnetoresistive sensor is arranged in the first clearance. The grounding alarm disclosed by the invention has the beneficial effects that the grounding alarm can be used for directly carrying out branch grounding failure detection, the detection accuracy, reliability and safety are high, installation at power failure is not needed, the equipment size is smaller, and the equipment is convenient to install.

Description

technical field [0001] The invention relates to a direct current grounding alarm, in particular to a direct current grounding alarm based on an opening current detector for on-line monitoring of grounding faults in a multi-branch power supply network, and belongs to the technical field of electric power. Background technique [0002] The DC system of power plants and substations is a complex multi-branch power supply network, which mainly provides power for secondary equipment such as automatic devices, relay protection screens, emergency lighting, and communication power supplies. The reliability of the DC system directly affects the safety of the entire power system, and the faults of the DC system are mainly ground faults. At present, the DC systems of power plants and substations mostly use 110V or 220V power supply, and the positive and negative busbars are floating to the ground. Therefore, when a ground fault occurs in the DC system, the DC system can still maintain n...

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Problems solved by technology

Therefore, the above ground fault detection methods in the prior art mainly have the following disadvantages: (1) Due to the use of distributed monitoring, only the insulation status of the entire system can be judged, and the specific grounding point cannot be directly determined, and the grounding method must be determined one by one. (2) When the grounding fault occurs on the charging equipment, the battery itself and the DC bus, it is difficult to find the grounding point with the method of pulling the road; (3) For rainy weather, two-point or multi-point grounding or multi-point virtual grounding In the case of poor insulation, it is difficult to find the grounding point with the method of pulling; (4) When the insulation resistance of the positive and negative poles of the DC system decreases equally to the ground, the DC insulation monitoring device used in the prior art cannot send out (5) In the process of using relevant instruments to check the ground faults of each branch one by one, if the clamp leakage current finder is used for investigation, since the clamp leakage current finder adopts the principle of differential current monitoring, when looking for the grounding point It needs to be checked manually one by one, and high-impedance grounding cannot be monitored, so the inspection cycle is long and there are potential safety hazards; Locate the grounding point, and this device is a closed coil, so it needs to be installed with power off, but it cannot be powered off during the operation of the equipment, and even if it is installed during the equipment outage maintenance period, due to the large number of equipment in the control cabinet and the complicated wiring, As a result, problems such as insufficient space in the control cabinet arise

However, there are usually the following defects: (1) In the prior art, Hall sensors are often used to detect the change of magnetic field strength in the closed loop caused by the leakage current of the branch circuit. Due to some inherent characteristics of the Hall element, it is difficult to meet such small Current detection and other application requirements, and when the detection processing circuit simply amplifies the Hall sensor signal, due to the low signal-to-noise ratio of the signal, the amplified small current signal will be submerged in the background noise, making it difficult to detect the target signal; (2) Leakage current detection modules that have appeared in the prior art usually use closed iron cores (or loop-shaped coils) to realize the aggregation of magnetic flux lines. Since the closed iron core and loop-shaped coils themselves are a closed structure, when using the leakage current When the detection module detects the leakage current of the branch circuit, in order to let the branch circuit pass through the closed closed iron core (or loop coil), it must be installed with power off, but it cannot be powered off during the operation of the equipment, which limits this structure The application of the leakage current detection module

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