The overvoltage wave invading the high and low voltage switchgear along the line can cause great harm to the edge of the equipment They must be limited to a reliable range that the equipment can withstand. This overvoltage wave may be the induced overvoltage caused by lightning activities near the transmission line, the operating overvoltage caused by the operation mode change, equipment input or exit operation in the system, or the overvoltage caused by lightning hitting the conductor outside the incoming line section. In order to clarify the working principle of lightning arrester, the process of limiting lightning overvoltage by tubular lightning arrester and silicon carbide lightning arrester is analyzed.

To release the energy of overvoltage It is necessary to connect J between the conductor and the earth Lightning arrester. The function of lightning arrester is: under normal conditions. It is in the cut-off state. When the overvoltage wave of wing over arrester protection level reaches The arrester turns on immediately, limiting the amplitude of overvoltage After the lightning flows into the earth, it is also necessary to cut off the power frequency current (called freewheeling) of the conductor flowing to the earth in the channel formed when the lightning current passes through the spark gap (referred to as gap), and then the arrester returns to the edge state.

Therefore, the working process of lightning arrester can be summarized into three steps: voltage limiting, arc extinguishing and recovery.

The voltage limiting effect of lightning arrester is first realized by gap. Figure 1-1 shows the waveform of voltage at both ends when the arrester acts It can be seen from the figure When the tubular arrester acts, the voltage is a cut-off wave, and then there is a high oscillation voltage for tens of milliseconds (several cycles). After the gap breakdown of the valve arrester, its terminal voltage does not drop to zero, but has a certain value of voltage drop. The voltage drop is generated when the lightning current flows through the nonlinear resistance, which is called residual voltage, which determines the protection level of the arrester.

The structures of arc extinguishing devices of different types of arresters are different. Gas producing materials are installed inside the tubular arrester It can generate high-pressure air break of the large dish when the Huo current passes, so as to blow off the arc. The gap of valve arrester must rely on the cooperation of its series nonlinear resistor to limit the freewheeling below a certain value in order to block it. The gap between 052 and 1056 of ordinary valve arrester is composed of upper and lower pieces of electricity. Under the current limiting action of low Ju fired SiC electric limiting plate The power frequency peak current (design value) of 50A and 80A can be interrupted accordingly. The gap of magnetic blow valve arrester has two structures: concentric rotating arc type and long arc current limiting type (due to the limiting effect of arc voltage drop on freewheeling) It is equipped with high-temperature fired SiC resistor (the FCD type class blow arrester designed in the early stage used 0250 low-temperature resistor). It can block the peak current of 300 - 800 a or even nearly kiloampere.

The recovery process of lightning arrester refers to the process of de dissociation in its gap. In this process, the ions and free electrons filled in the gap gas disappear rapidly, and the edge intensity is restored within a few milliseconds At this time, the gap is in the edge state again to ensure the normal operation of the power grid.

Taking the blowing arrester as an example, the changes of voltage and current in the whole working process are shown. The voltage limiting effect of gapless zinc oxide arrester is realized by ZnO Resistor. The volt ampere characteristic curve of ZnO Resistor is very different Under the working power limit, the leakage current is only in the order of Ma, and it is basically a capacitive component, close to the edge state. When overvoltage occurs, the resistance becomes small, which is convenient for releasing energy #o. After the energy is released, the resistor will return to the initial high limit state by itself. It can be seen that zinc oxide arrester does not produce arc in operation The whole process of its work only includes two steps: pressure limiting and recovery.