Device and method capable of distinguishing high-voltage motor overcurrent and overload protection action signals

Abstract

The invention provides a device capable of distinguishing overcurrent and overload protection action signals of a high-voltage motor and a method. According to the main technical scheme, a normally closed shutting contact for overload protection is additionally arranged in a logic loop for overcurrent protection; a series mode of normally open contacts of three overcurrent relays is adopted, the middle relay 2KM is directly started, a normally closed contact of the middle relay is used for shutting an overcurrent protection loop, and a normally open contact of the middle relay is used for starting a delay time relay 2KT loop for overload protection; switching is conducted on overload protection and a connecting piece LP through the signal relay 3KS, and two functions that overload protection acts on tripping, and only signals are sent while tripping does not occur can be achieved. Due to the fact that the action alarm signals for overcurrent protection and overload protection can be distinguished very clearly, consistency of overload protection is enhanced, and selectivity of overcurrent protection and overload protection can be stronger and clearer.

Description

technical field [0001] The invention belongs to the field of relay protection of electric power systems, and in particular relates to a simple method capable of clearly distinguishing overcurrent and overload protection action alarm signals of high-voltage motors. Background technique [0002] High-voltage motors are important electrical equipment in industrial enterprises, and are also the main driving equipment for process production devices. Due to various reasons, faults such as three-phase short circuit, two-phase short circuit and grounding short circuit may occur in the distribution cable of the high-voltage motor or the stator winding coil of the motor itself during production and operation, and the stator winding coil of the motor may also have a turn short circuit fault. If the production process load changes or other factors, it will also cause abnormal operation conditions such as overload or overload of the motor. [0003] Once the above-mentioned short-circui...

AI Technical Summary

Problems solved by technology

The second method is similar to the first method, except that there is no single-phase overload protection with time limit

However, when the process equipment of the production unit is suddenly seriously overloaded, the delay action time of the overload protection is one time longer than that of the overcurrent protection. △t , may not be able to operate correctly, but the over-current protection acts first to trip the circuit breaker of the motor, and correspondingly sends out an alarm signal for the action of the over-current protection

Once such a protection action signal is issued, it will naturally make people think that the power distribution unit of the motor or the internal winding of the motor has a short-circuit fault, which will mislead the process and electrical personnel to focus on the power distribution of the motor. Part of the inspection, but really neglected the inspection of production process equipment

The fact is that the overload is caused by the production process, not the power distribution part of the motor

Therefore, such a misleading action signal issued by the protection will not only delay the time of troubleshooting, but also expand the loss of the power outage accident.

Obviously, this kind of protection alarm signal cannot clearly distinguish the action characteristics of overcurrent and overload protection, of course it is wrong

[0012] The second protection method is not equipped with overload protection. Whether it is a short-circuit fault between turns of the motor winding or a serious overload, the over-current protection will trip and issue an over-current alarm signal.

[0014] It can be seen that the existing three protection methods for high-voltage motors, in the case of real overload, cannot clearly distinguish the over-current and overload signals, thus delaying the correct fault finding time and expanding the loss of power failure accidents

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