Advantages and disadvantages of single-phase parallel lightning arrester Pay attention to misunderstandings
May 23, 2022
Introduction to the advantages and disadvantages of single-phase parallel lightning arrester
1. Advantages: The circuit is simple, the composite symmetrical circuit is used, the common mode and differential mode are fully protected, and L and N can be connected at will.
2. Disadvantages: The varistor RV1 is prone to fire after short-circuit failure. It is best to connect a power frequency fuse in series with each varistor to prevent the varistor from short-circuiting and catching fire. If the L and N lines cannot be reversely connected, the varistors RV2 and RV3 can be omitted, and the upper end of the discharge tube G is directly connected to the N line to form a "1+1" circuit.
3. The varistor voltage value of the varistor is selected according to the following table (selecting a higher varistor voltage is safer, more durable, and has a lower failure rate, but the residual voltage is slightly higher). Or use several varistors in parallel (should select parallel varistors with similar voltages to extend service life and ensure safety).
4. The flow capacity of the ceramic gas discharge tube is selected according to the required flow capacity, and the DC breakdown voltage is 470V ~ 600V. When the flow capacity required by the arrester is ≤3KA, the glass discharge tube can be used instead.
5. Both the varistor and the gas discharge tube must calculate the flow capacity according to the derating value of more than 10 times of shock (the varistor is about one-third of the flow capacity of one shock, and the gas discharge tube is the maximum flow capacity of about half)
Consumers often have insufficient understanding when purchasing lightning protection devices, and there are many misunderstandings about lightning protection devices, resulting in improper selection. What are the precautions for purchasing a lightning protector?
The first point: the shape and size of the lightning arrester:
The shape and size of the arrester are related to the material of the valve plate used to manufacture the arrester. According to the use environment of the surge arrester, if the use space is large, it is not necessary to consider the size of the surge arrester; if it is used indoors, the size of the surge arrester should be considered: silicon carbide surge arrester SiC valve plate, unit flow capacity It is only 1/4 of the ZnO valve plate. Under the same flow capacity, the SiC valve plate has a larger diameter and the outer diameter of the surge arrester is also larger; under the same rated voltage and residual pressure conditions, the carbon surge protector is siliconized The height of the arrester is larger than that of the zinc oxide arrester.
The second point: the cost performance of the lightning arrester:
The valve plate of the gapless zinc oxide surge arrester is subjected to the action of the grid voltage for a long time, and the environmental conditions are harsh. The valve plate must be strictly inspected when it leaves the factory. The valve plate of the gapless zinc oxide surge arrester has a weak ability to withstand transient overvoltage and cannot be used in a 3-35kv power grid. For gap zinc oxide surge arresters used in series, the valve plate will not be damaged during long-term operation.
The third point: the service life of the lightning arrester:
The use environment, quality, durability and many other factors all affect the service life of the lightning arrester. The aging degree of the valve directly affects the service life of the lightning arrester. The gap valve plate of the series gap zinc oxide arrester is the most durable, the valve plate of the non-gap zinc oxide arrester is the second, and the life of the valve plate of the silicon carbide arrester is the shortest, generally 7-10 years, if the use conditions are harsh The service life will be greatly shortened. The comprehensive life of the valve plate of the series gap zinc oxide surge arrester is more than 20 years.