Protective device for electric system

Abstract

The invention relates to a protective device for an electric system. The protective device for the electric system comprises a delay type open circuit protective circuit, a negative temperature coefficient, a control switch and a rapid open circuit protective circuit, wherein the delay type open circuit protective circuit is used for carrying out open circuit protection on a circuit when the electric system has a short-circuit fault, and cannot carry out false operation on instant surge current of the electric system when the electric system is started normally, the negative temperature coefficient is used for restraining the surge current brought by charging of the capacitive load at the moment of starting, the control switch is turned off at the moment of starting of the electric system, is turned on after the starting of the electric system is accomplished, and is used for improving the surge current and eliminating influence caused by the negative temperature coefficient on conversion efficiency, and the rapid open circuit protective circuit can timely carry out operation to be opened when the electric system has the short-circuit fault, and enables the peak value of short-circuit fault current to be effectively restrained through the negative temperature coefficient. According to the protective device for the electric system, when a switch device has a short-circuit fault, the rapid open circuit protective circuit can also be timely opened to avoid impact damage caused by the surge current to devices of other portions, the protective characteristic of a power utilization system is comprehensively improved, and the defects of an existing electric power protective device are overcome.

Description

technical field [0001] The invention relates to the field of electric power, in particular to a power system protection device. Background technique [0002] In modern power systems, there are generally a large number of capacitive loads. Since the initial voltage of the capacitor is zero, the power system will charge the capacitor quickly during the start-up process and cause a huge surge current, which is harmful to the power supply system and the power system. All of them will cause great harm, and even the surge current will cause some devices to burn out, resulting in product failure. In order to suppress the surge current caused by capacitive load charging at the moment of starting up, the traditional simple method is to connect a negative temperature coefficient thermistor NTC (Negative Temperature Coefficient) in series in the input line, such as Figure 1 At the moment of system start-up, due to the large resistance of NTC, it will effectively limit the inrush curre...

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Problems solved by technology

[0003] The main purpose of the present invention is to provide a power system protection device, which aims to solve the current power system protection device because the equivalent impedance of the switchgear is extremely small and it is difficult to disconnect in time, and the short-circuit fault current is usually huge because there is no NTC current limiter, causing delays. The time-type open circuit protection device often does not act in time when a short-circuit fault occurs in the system, resulting in the tripping of single-stage or multi-stage air switches in the power supply system

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