ZnO resistor is the core element of the lightning arrester. It mainly protects power system equipment by limiting lightning overvoltage to ensure that the line does not trip. The performance indicators of ZnO resistors mainly include potential gradient, flow capacity and nonlinear coefficient, which are determined by the formula and process on the macro level and by the "ZnO grain-boundary layer" characteristics on the micro level.
ZnO grain: it is the main body of the resistance sheet, there is a small amount of cobalt (Co), manganese (Mn) and other elements in the solid solution accounting for more than 90% of the volume, and the size is 5-15 μ m. The resistivity is 0.001-0. l Ω. m and there is a small amount of cobalt (Co), manganese (Mn) and other elements in the solid solution.
Grain boundary layer: it is the enrichment area of dopants. The resistivity under a low electric field is greater than l00M Ω. m, and it is in the conduction state under a high electric field. The grain boundary layer is the source of pressure-sensitive characteristics.
Features of zinc oxide disc for Surge Arrester
Small current area: the resistance sheet presents a high resistance value, and the current flowing is below 1mA. The ratio of the inflexion point voltage to the thickness of the resistance sheet in this area is a potential gradient.
Non-linear area: It is the working area of the resistor. The flatter the U-I curve, the higher the non-linear coefficient of the resistor; The wider the range, the better the flow capacity.
High current area: the resistance sheet may be damaged when it enters the low resistance state.
