Characteristics of metal oxide resistors

Zinc oxide resistors have the following advantages:

a) Good protection characteristics

  Due to the excellent non-linear shape of the zinc oxide valve, the arrester can be designed without gaps. Its protection level (residual pressure) is the arithmetic sum of the residual pressure numbers of the series valve discs, and it has the characteristics of being stable and non-dispersed in the field of full current. The residual voltage at the milliampere level in the small current region is equivalent to the vicinity of the bend in volt-ampere characteristics. Its current varies with the area of ​​the valve disc. At present, the residual voltage under 1mA DC or AC is generally used at home and abroad. Ultra-high voltage and high-energy arresters are useful for 3mA or 5mA (such as multiple parallel connection). The resistance of the arrester at normal operating voltage is very large, which is similar to an insulator, and its conductance current is micro-amps (tens of micro-amps). The medium current area is the residual voltage under operating surge current. The high current area is the residual voltage under lightning impulse current. It can be seen that from small current to large current shows a relatively flat residual voltage. In the actual operating system, the arrester is subject to AC voltage, operating overvoltage and lightning overvoltage. The excellent non-linear characteristics of the zinc oxide arrester can achieve the lightning overvoltage and operating overvoltage required by high-voltage and ultra-high voltage power equipment. Good level of protection in cooperation with the area. This can reduce the insulation level of the power system and obtain great economic benefits

b) Large flow capacity

     Compared with the silicon carbide valve, the zinc oxide valve has a flow capacity of about four times larger per unit area. In ultra-high voltage and ultra-high voltage power systems, the operating overvoltage is the main factor that determines the insulation level of the system. It requires that the energy released by the arrester becomes larger and larger. The silicon carbide arrester cannot meet the demand, and the zinc oxide arrester can be realized.