A lighting arrestor is a device used to protect electrical equipment from lightning to direct abnormal high voltage to the ground without affecting the continuity of power supply to the circuit, also used to limit operating overvoltage.
The lighting arrestor is used to protect the insulation of AC power transmission and transformation equipment from lightning overvoltage and operating overvoltage damage. It is suitable for over-voltage protection of transformers, transmission lines, distribution panels, switchgear, power metering boxes, vacuum switches, parallel compensation capacitors, rotating motors and semiconductor devices.
In a power system, arresters are installed in parallel. When the overvoltage value reaches the specified operating voltage, the arrester immediately action, current, limit the overvoltage amplitude, protect the equipment; After the voltage becomes normal, the arrester quickly recovers to ensure normal power supply to the system.
There are three basic types of lighting arrestor:
Tube arrester: a protective gap with high arcing capacity, consisting of two series gaps.
Valve arrester: composed of spark gap and valve resistance, valve resistance is made of special silicon carbide. Silicon carbide valve resistance can effectively prevent lightning and high voltage, to protect equipment.
Zinc oxide arrester: mainly composed of zinc oxide varistor, it mainly uses zinc oxide good nonlinear voltammetry characteristics, so that the current flowing through the arrester at normal working voltage is very small (microampere or milliampere level); When the overvoltage action, the resistance drops sharply, the release of voltage energy, to achieve the effect of protection.
The material of zinc oxide arrester is "polymer silicone rubber". Compared with porcelain arrester under the same conditions, the flashover voltage is more than 2 times that of porcelain arrester. Therefore, the integrated composite zinc oxide arrester has become the mainstream products, widely used in the international power system. By silicone rubber with flame retardant, anti-aging agent, coupling agent vulcanized by high temperature and high pressure. Zinc oxide arrester type is divided into YH5WS (distribution type), YH5WZ (power station type), YH5WR (capacitive type), YH5CS (series gap), YH1.5W (neutral point type), YH5WX (line type).
How can a zinc oxide lighting arrestor do the lighting protection?
Lightning protection components by zinc oxide varistor, insulation support, gasket, pressure relief devices, etc, zinc oxide varistor is a multicomponent polycrystalline ceramic semiconductor, internal hole, zinc oxide varistor is zinc oxide is given priority to, and added a small amount of metal additives, after mixing them sufficient granulation forming, the high temperature roasting.
A varistor is a voltage limiting element that is sensitive to changes in voltage, or a resistor whose value is sensitive to voltage.
Its characteristic is: at the specified temperature, when the voltage exceeds a critical value, its resistance value will sharply decrease, the current through it sharply increase, voltage and current do not show a linear relationship. Therefore, varistors are also called nonlinear rheostat.
Resistance material is semiconductor, zinc oxide varistor is a polycrystalline semiconductor ceramic component made of zinc oxide as the main body, doped with a variety of metal oxides, using typical electronic ceramic process.
There are 7 characteristics of zinc oxide lighting arrestor:
Current capacity: ability to absorb various lightning overvoltage, power frequency transient overvoltage and operating overvoltage
Protection characteristics: Protect various electrical equipment in power system from voltage damage because of the excellent nonlinear voltammetry characteristics of zinc oxide valve plate
Sealing performance: adopt high quality compound coat to ensure reliable sealing and stable performance of lightning arrester
Mechanical properties: stable
Decontamination performance: high
High reliability of operation: the reliability of long-term operation depends on product quality and reasonable product selection
Power frequency tolerance: ability to withstand a certain power frequency voltage rise in a certain period of time.