Structural characteristics Surge arrester

The basic structure of metal oxide arresters are valves [52], the valve with a zinc oxide (ZnO) as the main material, doped with small amounts of other metal oxide additives, high temperature roasting, varistor has a good non-linear characteristic , so called sensitive arrester.
The basic structure of this sintered body of zinc oxide grains in the high conductance [53], a resistivity of 1 Ω⋅ cm. Edge made of high-resistance (mainly metal oxide additions) surrounded by grain boundary layer, the resistivity is about 1010 ~ 1014Ω⋅cm at low electric field strength. At higher voltage is applied, the grain boundary layer of metal oxide varistor symboladditions to the valence electrons are pulled out, or because electron avalanche impact ionization of carriers leaving a significant increase [54]. When the electric field strength reaches 104 ~ 105V / cm, resistivity that is down to 1 Ω⋅ cm; when the applied voltage is reduced role, since the composite that carriers reduce resistance and bigger, so it has good nonlinear. And it is non-linear voltage characteristics in the positive and negative polarity is symmetrical.
Metal oxide valve under normal operating voltage through the resistive current is small, typically about 10 ~ 15μA, close to the insulating state. When acting on the valve voltage increases, current increases. The valve plate by resistive current of 1mA, the effect on the arrester voltage mA U1 as a starting operating voltage. Because zinc oxide valve has a good nonlinear characteristics, in the ratio by 10kA impulse current residual voltage and mA U1 is generally not more than 1.9, the pressure ratio is smaller, the better the performance of its protection. value mA U1 is about the maximum allowable operating voltage peak of 1.05 to 1.15 times.