Voltage acceleration inverse time-delay over-current protection method used for micro power grid

Abstract

The invention relates to the field of distribution network relay protection of an electric power system and relates to a voltage acceleration inverse time-delay over-current protection method used for a micro power grid. According to voltage and current information acquired by a protection mounting point, after a short circuit fault occurs and is judged to be a positive directional fault, a method for calculating protection time-delay operation time comprises the step of multiplying an existing inverse time-delay over-current protection setting formula by a voltage accelerated factor to obtain an accelerated operation time, wherein the minimum value of per-unit values of three phase voltages and three line voltages at the protection mounting point is taken as the voltage accelerated factor. The voltage acceleration inverse time-delay over-current protection method used for the micro power grid has the advantages that the time for eliminating the short circuit fault at line exit is very short, the delay-free operation is achieved, the faults at other points on the line and various faults also can be quickly processed, and the demand on rapidity is met.

Description

technical field [0001] The invention relates to the field of relay protection for power system distribution networks, and proposes a voltage acceleration inverse time-limit overcurrent protection method for micro-grids. Background technique [0002] With the development of distributed generation technology (distributed generation), more and more distributed power sources are connected to the grid. The way distributed power is connected to the microgrid (grid-connected operation state) is currently the best way to effectively utilize distributed power. The microgrid can operate in the grid-connected or isolated state, and its connection to the grid will bring new problems to the relay protection of the power system, resulting in the deterioration of the traditional protection performance and failing to meet the requirements of relay protection. At present, the low-voltage distribution network at home and abroad mostly adopts inverse time overcurrent protection as its main pr...

AI Technical Summary

Problems solved by technology

The microgrid can operate in the grid-connected or isolated state, and its connection to the grid will bring new problems to the relay protection of the power system, resulting in the deterioration of the traditional protection performance and failing to meet the requirements of relay protection

At present, low-voltage distribution networks at home and abroad mostly adopt inverse time overcurrent protection as its main protection principle, which is greatly affected by the connection of micro-grids, resulting in long operating time and unsatisfactory selectivity.

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