Seven major characteristics of zinc oxide arrester:
1. Large current carrying capacity
This is mainly reflected in the arrester's ability to absorb various lightning overvoltages, power frequency transient overvoltages, and switching high voltages. The current carrying capacity of zinc oxide arresters fully meets or even exceeds national standards. Indicators such as line discharge class, energy absorption capability, 4/10 nanosecond high current impulse withstand, and 2ms square wave current carrying capacity have reached the domestic leading level.
2. Excellent protection characteristics
Zinc oxide arresters are electrical products used to protect various electrical equipment in power systems from overvoltage damage, and they have good protective performance. Because the nonlinear volt-ampere characteristics of zinc oxide valve plates are excellent, only a few hundred microamperes of current pass through under normal operating voltage, making it easy to design a gapless structure, which gives it the characteristics of good protection performance, light weight, and small size. When overvoltage intrudes, the current through the valve plate increases rapidly, while limiting the amplitude of the overvoltage and releasing the energy of the overvoltage. Afterward, the zinc oxide valve plate returns to a high-resistance state, allowing the power system to operate normally.
3. Good sealing performance
The arrester components use high-quality composite jackets with good aging resistance and air tightness, and measures such as controlling the compression of sealing rings and applying additional sealing adhesive are adopted. The ceramic jacket is used as a sealing material to ensure reliable sealing and stable performance of the arrester.
4. Mechanical performance
The following three factors are mainly considered:
(1) Earthquake force it can withstand
(2) Maximum wind pressure acting on the arrester;
(3) Maximum allowable tension of the conductor that the top of the arrester can bear.
5. Good anti-pollution performance
Gapless zinc oxide arresters have high pollution resistance.
The creepage distance ratio levels specified by national standards are:
Class II Medium pollution area: creepage distance ratio 20mm/kV
Class III Heavy pollution area: creepage distance ratio 25mm/kV
Class IV Extra heavy pollution area: creepage distance ratio 31mm/kV
6. High operational reliability
The reliability of long-term operation depends on the quality of the product and whether the product selection is reasonable. The product quality is mainly affected by the following three aspects:
(1) The rationality of the overall structure of the arrester;
(2) The volt-ampere characteristics and aging resistance of zinc oxide valve plates;
(3) The sealing performance of the arrester.
7. Power frequency withstand capability
Due to various reasons in the power system such as single-phase grounding, long-line capacitance effect, and load shedding, power frequency voltage rise or transient overvoltages with high amplitude may occur. The arrester has the ability to withstand a certain level of power frequency voltage rise for a certain period of time.
