Small current earthing wire selection protection apparatus and protection method based on GPRS

Abstract

The invention relates to a GPRS-based protection device of small-current grounding line selection and a protection method thereof. The protection method adopts zero-sequence compensation admittance line selection method. One device realizes the protection of the small-current grounding line selection under NUS and NES connection mode in a compatible way, thereby broadening the scope of application. Simultaneously, the protection device provides a switch output signal to the outside, and the GPRS wireless network is used for wireless communication. In the method, the judgment conditions for failure judgment under the condition of the NUS connection mode are increased; the errors are greatly reduced; the line selection accuracy is further improved; the misjudgment rate of the device is reduced and is lower than 1 percent under the ideal conditions; the misjudgment rate in the site test can be maintained within 5 percent; the device has the advantages of high reliability and long transmission distance; and the utilization of the GPRS module can reduce the construction cost, accelerate the access to the network and provide reliable communication.

Description

technical field [0001] The invention belongs to the field of power transmission, is applied to a neutral point ungrounded power grid, and is a GPRS-based small current grounding line selection protection device and a protection method. Background technique [0002] When single-phase grounding occurs in the neutral point indirect grounding grid, also known as the small grounding current system, since the current at the fault point is very small, and the line voltage between the three phases remains symmetrical, it has no effect on the load power supply. Therefore, Under normal circumstances, it is allowed to continue to run for another 1 to 2 hours without tripping immediately. However, after a single phase is grounded, the voltage of the other two phases to ground increases In order to prevent the fault from further expanding into a two-point or multi-point grounding short circuit, the operating personnel should take timely measures to eliminate it. [0003] The neutral p...

AI Technical Summary

Problems solved by technology

When a small current grounding fault occurs in the power distribution network, it is impossible to detect and take effective preventive measures in advance, and the accurate location of the grounding point can only be determined by the method of pulling the road and the method of manual inspection and visual inspection afterwards. The road pulling method requires a lot of The switching operation caused great loss to the production, especially for the continuous operation production area and some key equipment; after the accident, it took a lot of time to find the grounding point by manual line inspection and visual inspection. Manpower, material resources and time

At present, some technicians have done a lot of research and development work on this, and developed a protection device that uses the method of group ratio, amplitude ratio, and phase ratio, but due to the influence of the unbalanced current and operation mode of the zero-sequence current transformer, the judgment is unstable

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