The difference between zinc oxide arrester and elbow arrester

The difference between zinc oxide arrester and elbow arrester

1. (1) Working principle of valve-type arrester:
When the system is normal, the spark gap isolates the valve plate resistance from the working bus, so as not to burn out the valve plate resistance due to the current generated in the valve plate resistance by the working voltage.
Once the voltage on the working bus exceeds its breakdown voltage value, the spark gap will be broken down and lead the lightning current to leak into the earth through the valve plate resistance. At this time, the resistance value of the valve plate resistance will automatically decrease to reduce the resistance at its two ends. The residual pressure formed.
After the lightning current disappears, the voltage acting on the valve plate resistance is the power frequency voltage. At this time, the resistance value of the valve plate resistance will automatically increase, limiting the power frequency freewheeling to prompt the arc to be quickly and reliably extinguished.

(2) The valve arrester is composed of multiple spark gaps and valve plate resistors in series.
The distance between the spark gap is small, the electric field is similar to the uniform electric field, the volt-second characteristic is relatively flat, and the insulation coordination is easy to realize. In addition, multiple gaps make the arc segmented when the power frequency continues to flow. Compared with the long arc, the short arc is easier to cut, and the recovery ability of the gap insulation strength is improved.
The existence of valve plate resistance avoids clipping waves that are unfavorable to insulation. Its non-linearity makes it show low resistance when passing lightning current to limit the residual voltage of the arrester and improve the protection performance; when passing power frequency freewheeling, it shows high resistance and the voltage is constant to limit power frequency freewheeling and improve arc extinguishing performance.

2. (1) Working principle of zinc oxide arrester:
Under the action of the working voltage, the current flowing through the ZnO valve is much less than 1mA (the main component is the capacitive current), which is equivalent to an insulator and will not burn the valve, so the working voltage can be isolated without a series gap.
When the voltage applied to the ZnO valve exceeds a certain value (initial operating voltage U1mA), “on” will occur. After “on”, the resistance of the ZnO valve is very small, and the residual voltage is related to the current flowing through it. Basically irrelevant.
When the applied voltage drops below the operating voltage, the “on” of the ZnO valve plate is terminated, which is equivalent to an insulator, so there is no power frequency freewheeling.
This is the reason why MOA can achieve seamless flow without freewheeling. (The lightning current becomes an insulator in the past, so only the lightning current passes through the ZnO valve plate)
Compared with silicon carbide SiC valves, ZnO valves have ideal nonlinear volt-ampere characteristics.

(2) Compared with the traditional arrester composed of SiC valve disc and series gap, zinc oxide gapless arrester has the following advantages:
①Simple structure, suitable for large-scale automated production, small size, light weight and low cost.
② Superior protection performance. Because the ZnO valve has excellent volt-ampere characteristics, the residual voltage is lower; it can release energy during the entire overvoltage period, and there is no spark, so there is no discharge time delay, and it has good steep wave response characteristics, especially suitable for GIS Protection of gas insulated substations and DC systems.
③Strong ability to withstand repeated actions, only absorb over-voltage energy, no need to absorb freewheeling energy.
④Large flow capacity. The flow capacity per unit area of the ZnO valve is 4 to 5 times that of the SiC valve. It can be used as a backup protection for internal overvoltage.
⑤Good stain resistance. Since there is no series gap, the problem of unstable discharge voltage of the series spark gap due to uneven pollution on the surface of the porcelain sleeve can be avoided, and it is easy to manufacture anti-pollution and live-cleaning arresters. (Not affected by surface contamination)