Method for preventing low-voltage protection misoperation of motor caused by PT disconnection

Abstract

A method for preventing low-voltage protection misoperation of a motor caused by PT disconnection belongs to an emergency protection field. Disconnection faults of a first side and a second side of PT are monitored in real time simultaneously by adopting the method of monitoring the open-delta voltage of PT, monitoring whether high-voltage fuse fuses and monitoring the voltage of the second side of PT. Once it is discovered that disconnection faults occur at the first side and the second side of PT, a latching control signal is outputted immediately. Low-voltage protection output loops of each motor on the same busbar are disconnected and latching protection is carried out. At the same time a second loop of a small busbar of the voltage is disconnected and self-locking of the latching control loop of PT disconnection is carried out. The technology scheme can reflect PT secondary disconnection faults more reliably and directly and the latching mode is safer. No adoptive equipment obtain electricity in normal operation, and the method is in favor of long-term reliable operation of equipment and can prevent low-voltage protection misoperation of motor effectively.

Description

technical field [0001] The invention belongs to the field of emergency protection of power systems, and in particular relates to a protection locking method for power supply systems. Background technique [0002] With the continuous development of industrial enterprises, the number of motors used in factories is increasing. As of the end of 2009, the total installed capacity of electric power in the country reached 874 million kilowatts. While using a large number of motors, higher requirements are placed on the configuration of motor relay protection. . [0003] According to the provisions of No. 9.0.5 of GB50062-1992 "Code for Design of Relay Protection and Automatic Devices for Electric Power Devices", the voltage of the busbar (busbar refers to the busbar for the primary circuit of the motor, also known as the high-voltage busbar, the same below) voltage drops or is interrupted for a short time. Motor low-voltage protection should be installed and act on tripping. [0...

AI Technical Summary

Problems solved by technology

[0009] However, the disadvantage of this control method is that the low-voltage relay YJ senses the high-voltage bus power supply. Not only is the high-voltage power likely to cause equipment damage, it is difficult to implement from the perspective of power safety, and signal sampling is unreliable. Wiring narrows the safe distance from the high-voltage bus, which is prone to serious accidents such as phase-to-phase short circuit of the bus, which may cause power trips in the substation area, or cause casualties and equipment damage, which will bring great harm to the safe operation of the factory power supply system. Hidden danger

[0011] The disadvantage of this method is that for substations with a large number of electric motor loads, the blocking voltage protection through the current signal cannot directly reflect the PT disconnection fault, the blocking logic is complicated, the secondary wiring circuit is cumbersome, and it is limited by the following The configuration of electrical protection devices requires a large investment and has great limitations

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