A lightning or release and can release the power system operation over voltage energy, protect electrical equipment from transient overvoltage, and can cut off the continued flow, not to cause electrical system grounding (see photo). Lightning arrester is connected between the live wire and the ground, and the protected devices in parallel. When the voltage reaches a value specified when operating voltage, lightning arrester of immediate action, through the charge, to limit the voltage amplitude, protection equipment insulation; when the normal voltage, lightning arrester and quickly to restore the status quo, to ensure the normal power supply.
Lightning arrester most primitive is angular clearance, appeared in the late nineteenth Century, for overhead transmission line lightning damage, prevent equipment insulation caused power outages, so called "lightning arrester". Nineteen twenties, the aluminum oxide arrester, the arrester and pill type arrester. 30 in a tube type arrester. 50 in a silicon carbide arrester. 70's and the emergence of metal oxide arrester. Modern high-voltage surge arresters, not only used to limit the overvoltage caused by lightning in the power system, but also used to limit the overvoltage caused by system operation.
Lightning arrester tube and valve type two categories. Valve type lightning arrester is divided into silicon carbide valve type lightning arrester and metal oxide arrester (also known as zinc oxide lightning arrester).
Tube type arrester structure principle of figure. Internal clearance (also called arc gap) in gas production material in the arc tube, the outer gap separates the tube and power grid. Lightning over voltage that the inner and the outer gap, gap arc temperature in gas production material to produce gas, pipe pressure increases rapidly, high pressure gas sprayed from the nozzle arc. Tube type arrester has a larger impact flow capacity, available in the amplitude of lightning current big place. But the tube type arrester discharge voltage is higher and the dispersed, action is generated when clipping, less protection. Mainly used for protection of substation, power plant into the line protection and line insulation.
Silicon carbide arrester and its basic work elements are stacked to seal the spark gap and silicon carbide valve in the porcelain bushing (high voltage arrester product has multiple sections of porcelain). The main function of the spark gap is usually the valve plate and the charged conductor isolation, over voltage discharge and cut off the power supply of afterflow. The spark gap silicon carbide arrester by many gaps in series, discharge dispersion of small, volt-second characteristic flat, arc extinguishing performance. Silicon carbide valve with electrical silicon carbide as the main body, and the binder mixture, nonlinear resistor by pressing, sintering, the shape of a pie. The main effect of silicon carbide valve is to absorb over-voltage energy, using the nonlinear resistance (resistance to high voltage and high current declines sharply) limit the discharge current through the pressure drop (known as the residual pressure) and limit the continued flow amplitude, in coordination with the spark gap effect of freewheeling arc extinction. Silicon carbide arrester according to different structure, is divided into ordinary valve type and magnetic blowout valve type two. The latter uses a magnetic field to improve the arc extinguishing performance driven arc, so it has better protective performance. Silicon carbide surge arresters to protect the good performance, are widely used in AC, DC system insulation protection, substation, power generation equipment.
Metal oxide arrester and its basic element is a zinc oxide valve plate sealing in the porcelain sleeve. Zinc oxide valve sheet is ZnO as the matrix, adding a small amount of Bi2O3, MnO2, Sb2O3, Co3O3, Cr2O3 made of nonlinear resistor, nonlinear current-voltage characteristics are much better than silicon carbide, the leakage current flowing through the microampere level only in constant working voltage, action without the continued flow. So the metal zinc oxide arrester without gap, so the structure is simplified, and has fast response, resistant to multiple lightning over voltage or overvoltage effect, large energy absorption capacity, contamination resistance performance etc.. Because of the metal zinc oxide arrester protection performance is better than that of silicon carbide arrester, has been gradually replaced by silicon carbide arrester, widely used in AC, DC system insulation protection, substation, power generation equipment, especially suitable for effectively neutral grounded (see neutral grounding of power system) of 110000 kV and above power grid.
