Seven major characteristics of zinc oxide arresters:
1. Large current 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 capacity of zinc oxide arresters fully meets or even exceeds national standards. Indicators such as line discharge level, energy absorption capacity, 4/10 nanosecond high current impulse withstand, and 2ms square wave current capacity have reached the domestic leading level.
2. Excellent protective characteristics
Zinc oxide arresters are electrical products used to protect various electrical equipment in power systems from overvoltage damage, with good protective performance. Because the nonlinear volt-ampere characteristics of zinc oxide valve plates are excellent, only a few hundred microamperes of current pass under normal working voltage, making it easy to design a gapless structure, which gives it the characteristics of good protective performance, light weight, and small size. When overvoltage intrudes, the current flowing through the valve plate increases rapidly, while limiting the amplitude of the overvoltage and releasing the energy of the overvoltage. After that, 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 outer sheaths with good aging resistance and air tightness. Measures such as controlling the compression of sealing rings and applying sealing adhesive are adopted. The ceramic outer sheath serves as the sealing material, ensuring reliable sealing and stable performance of the arrester.
4. Mechanical performance
Mainly consider the following three factors:
(1) Earthquake force it can withstand
(2) Maximum wind pressure acting on the arrester;
(3) Maximum allowable tensile force of the conductor borne by the top of the arrester.
5. Good anti-pollution performance
Gapless zinc oxide arresters have high pollution resistance.
The creepage distance ratio levels specified by national standards are:
Level II Medium pollution area: creepage distance ratio 20mm/kV
Level III Heavy pollution area: creepage distance ratio 25mm/kV
Level 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 can rise or transient overvoltages with high amplitude can occur. The arrester has the ability to withstand a certain increase in power frequency voltage for a certain period of time.
