Undisturbed stable switching method for industrial enterprise factory electrical system

Abstract

The invention provides an undisturbed stable switching method for an industrial enterprise factory electrical system. The switching among a main feeder line, a standby feeder line and a bus coupler of a factory electrical system is controlled by an undisturbed stable control device comprising a CPU module, and a load is switched to a standby line. The method comprises the following steps of recognizing a running mode, starting a start mode, selecting a switching mode and judging according to the switching action process and a realizing way. The invention can prevent running voltage interruption or equipment impact damage caused during power supply switching, simplify the power supply switching operation and reduce misoperation, thereby ensuring the power-on continuous running of electrical equipment.

Description

technical field [0001] The invention relates to a method for switching an electric power system, in particular to a method for switching a power system of an industrial enterprise without disturbance and stably. Background technique [0002] There are a large number of electrical equipment installed in the power grid. Due to the huge power grid, it is greatly affected by the natural environment, there are many devices, and the probability of failure is high. It is prone to short-term interruption of power supply. Since the medium voltage of chemical and steel enterprises is generally an ungrounded system, However, due to the large system and the large capacitive current of the system, although the arc suppressing coil is installed, it often develops into a multi-phase short circuit after a single-phase grounding occurs, and the bus voltage will fluctuate rapidly; at the same time, due to the needs of the production process, it is often equipped with a large-capacity rectifier...

AI Technical Summary

Problems solved by technology

[0002] There are a large number of electrical equipment installed in the power grid. Due to the huge power grid, it is greatly affected by the natural environment, there are many devices, and the probability of failure is high. It is prone to short-term interruption of power supply. Since the medium voltage of chemical and steel enterprises is generally an ungrounded system, However, due to the large system and the large capacitive current of the system, although the arc suppressing coil is installed, it often develops into a multi-phase short circuit after a single-phase grounding occurs, and the bus voltage will fluctuate rapidly; at the same time, due to the needs of the production process, it is often equipped with a large-capacity rectifier Transformers, there are a lot of harmonics in the system, which cause interference to relay protection devices and automatic control equipment, and increase the failure rate of equipment, resulting in abnormal fluctuations in the power supply system; 400V protection is often thermal coupling and fuse protection, and the fault removal time is long ( Generally more than 200mS); when there are a large number of groups of self-starting motors in the system, the starting current is often very large (may cause protection malfunctions sometimes), and there are large fluctuations in bus voltage and long time; for some large enterprises, in order to ensure the reliability of power supply, the middle The voltage system operates in parallel, any equipment failure in the system will cause power fluctuations, the more equipment there is, the higher the probability of voltage fluctuations

[0003] When the system voltage fluctuates greatly due to the above reasons, it is very easy to cause some equipment on the bus section to stop abnormally, so that the process flow is abnormal, or even the process is terminated, resulting in production disorder

For the motor in the system, when the voltage drops below 70%, its output will drop below 50%, which will affect the normal process of the process. Many devices are equipped with 0.5S low-voltage protection. When the system is abnormal , even if the system is ready for automatic switching to act accurately (the busbar voltage loss delay is often longer than the overcurrent time, that is, the switching time is greater than 0.5S, and is greater than the AC contactor power-off trip time), that is, even if the switching is successful, the low voltage of 0.5S The protection has also been activated. At the same time, when the system has a large number of self-starting motors in groups, the self-starting current is often particularly large (sometimes may cause protection malfunctions), and there are large bus voltage fluctuations and long periods of time.

For example, it is easy to cause the synchronous motor to stop running due to out-of-step, loss of magnetism, and low-voltage action. At this time, the backup power supply can only be used as a security power supply, and the production process will be interrupted, posing a great hidden danger to production safety.

[0004] For small and medium-sized chemical companies, since there are not a large number of high-voltage motors, when the voltage fluctuations occur in the system, the residual voltage of the bus decays very quickly, that is, the system’s ability to resist voltage fluctuations is poor. The characteristics of the AC contactor are: the return voltage is 30% to 70%, and the AC contactor is disconnected within 60-80mS. The voltage fluctuation caused by various reasons can easily cause the AC contactor to separate abnormally. The production process there will be an interruption

[0005] For the synchronous motors in the system, because the excitation power is often from the same power source, when the power supply fluctuates, it is very easy to have a demagnetization protection action; when the power supply voltage fluctuates, it is very easy to cause the synchronous motor to lose its step, causing the synchronous motor to quit running; in addition When the power supply fluctuates for a long time, the low voltage protection will act, causing the synchronous motor to quit running

Synchronous motors and other important motors are out of operation, which will cause great hidden dangers in production safety, and even lead to serious production safety accidents

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