Identification method of fault current in starting process of asynchronous motor

Abstract

The invention discloses an identification method of fault current in a starting process of an asynchronous motor. The method comprises the following steps: (1) carrying out high-speed digital sampling on voltage and current of the asynchronous motor and forming a sampling data sequence of representing voltage and current change processes; (2) reconstructing equivalent BH curves of an iron core and an air gap between a stator and a rotor of the asynchronous motor through combined application of voltage and current data of the asynchronous motor, and calculating the slopes of the ellipse long-axis directions of the equivalent BH curves; and (3) identifying the starting current and the fault current during a startup period according to the change of the slopes of the ellipse long-axis directions of the equivalent BH curves. According to the identification method, the starting current and the fault current in the starting process can be effectively identified; the fault identification sensitivity in the starting process is improved; and the action time is shortened.

Description

technical field [0001] The invention belongs to the technical field of electric power systems, and in particular relates to a fault current identification method in the starting process of an asynchronous motor. Background technique [0002] High-voltage motors larger than 2000kW are usually equipped with differential protection. If a fault occurs during the start-up process, the differential can act sensitively and reliably to ensure the operation of the motor. The protection setting is set according to avoiding the starting current of the motor, and acts on the trip. The high-voltage asynchronous motors of some industrial and mining enterprises have set the inverse time overcurrent protection function and acted on tripping. However, due to the difference in the starting characteristics of the motor and the nature of the process, the inverse time overcurrent protection often occurs during the starting process or self-starting process of the asynchronous motor. Malfunctio...

AI Technical Summary

Problems solved by technology

The high-voltage asynchronous motors of some industrial and mining enterprises have set the inverse time overcurrent protection function and acted on tripping. However, due to the difference in the starting characteristics of the motor and the nature of the process, the inverse time overcurrent protection often occurs during the starting process or self-starting process of the asynchronous motor. Malfunction affects the production operation. When the asynchronous motor starts, the inverse time overcurrent protection function of the motor needs to be withdrawn to meet the motor start, and even the inverse time overcurrent protection function has been disabled for a long time, so the inverse time overcurrent protection cannot be reliable. put into operation

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