Intelligent tripping method for power supply lightning arrester

Abstract

The invention discloses an intelligent tripping method for a power supply lightning arrester. In the method, the power supply lightning arrester is connected to an alternating-current power supply through an electronic relay or a magnetic latching relay. As shown in a figure, intelligent tripping is realized through a leakage current sensing circuit, a data processing circuit, a sampling keeping circuit, an analog to digital conversion circuit, a control circuit, a driving circuit and the like, the leakage current sensing circuit is used for sensing the leakage current of the power supply lightning arrester in real time, the data processing circuit and the analog to digital conversion circuit are used for converting a leakage current signal into a digital signal, and the control circuit is used for judging according to a monitored result of the leakage current and automatically tripping a deteriorated power supply lightning arrester.

Description

technical field [0001] The invention relates to an intelligent method for disconnecting a zinc oxide varistor in a power arrester from a circuit after deterioration. Background technique [0002] The power surge arrester is a kind of surge voltage protector (also known as lightning arrester or surge protector, Surge Protective Device, referred to as SPD, mainly used for the protection of lightning strike voltage or instantaneous overvoltage of circuits and systems), mainly used for 380V / Surge protection for 220V power frequency AC power supply. The key components of the power surge arrester are zinc oxide varistors (Varistor: referred to as varistors). This kind of power surge arrester has a disadvantage. The leakage current will increase, so the zinc oxide resistor body will generate heat, and in severe cases, an arc will be generated to cause it to spontaneously ignite. If the degraded power arrester is not disconnected from the circuit in time, there is a danger of fire...

AI Technical Summary

Problems solved by technology

[0003] This physical protection method has the following deficiencies: 1. Time-lag of tripping: the degraded varistor needs a long delay from the initial moment of deterioration to the temperature rise required for the tripping action , due to the thermal inertia of the terminal and low-temperature solder, the temperature rise of the terminal lags behind the temperature rise of the zinc oxide varistor, so the action speed is slow; 2. The complexity of design and manufacture: During the manufacturing process, the elastic performance of the spring lever mechanism will be affected. Discrete changes occur, and the thermodynamic properties of low-temperature solder are also discrete, which often makes it difficult for the designed fixed torque matching to adapt to the discrete changes in the performance of specific products, resulting in improper matching of the traction torque and resistance torque of the spring lever mechanism of a certain product , even if the temperature rise reaches the specified value after the varistor deteriorates, the spring lever mechanism may not be able to pull the power terminal apart, so accidents that cause SPD spontaneous combustion often occur, and the opposite extreme is due to the traction torque of the spring lever mechanism If the configuration is too strong, the tripping will occur in advance, resulting in the waste of undeteriorated arresters; 3. The correlation between the tripping point and the use environment: the zinc oxide varistor will generate heat after deterioration, and the temperature will rise, and the value of the temperature rise The size of the zinc oxide varistor is related to the calorific value of the zinc oxide varistor, and it is also related to the ambient temperature. The low-temperature solder responds to the deterioration of the zinc oxide varistor under different conditions of use by preparing a fixed melting point of the metal mixture. This treatment is Inaccurate, unable to timely or accurately determine whether the SPD is damaged. When the ambient temperature is high, the tripping action will occur in advance, resulting in a waste of resources. In contrast, when the ambient temperature is low, the tripping will be delayed. Action, unable to trip the degraded varistor in time, resulting in failure of overvoltage protection

The patent "an intelligent power surge arrester" (ZL200710104342.8), which I invented in 2007, proposes to realize the intelligent tripping of the varistor by monitoring the temperature of the varistor. However, the said invention patent also has shortcomings: the pressure sensitive It takes a long time for the temperature to rise to the monitorable range after the resistance deteriorates, so the trip and alarm are not timely. On the other hand, the temperature sensor is embedded in the SPD and cannot be taken out for reuse, resulting in waste of cost; The leakage current of the varistor is very small, and it is difficult for the current transformer to directly sense the leakage current of the piezoresistor due to the limitation of sensing sensitivity. Therefore, based on the above-mentioned deficiencies of the prior art, the present invention provides a method for real-time monitoring of zinc oxide by differential method. The method of realizing intelligent tripping based on varistor parameters

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