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The Use Of Lightning Arresters
- May 10, 2018 -

1. Should be installed near the distribution transformer side.

The metal oxide arrester (MOA) is connected in parallel in normal operation, connected with the upper end and grounded on the lower end. When the circuit is overvoltage, the distribution of the transformer will withstand the three partial pressure drop caused by the overvoltage through the arrester, the lead wire and the grounding device, which is called residual pressure. In these three parts of overvoltage, the residual pressure on the arrester is related to its own performance, and its residual pressure value is certain. The residual pressure on the grounding device can be eliminated by connecting the grounding wire to the matching shell and then connected to the grounding device. The key to protect the distribution is to reduce the residual pressure on the leads. The impedance of the lead wire is related to the current frequency, the higher the frequency, the stronger the inductance of the wire and the greater the impedance. From U = IR, to reduce the residual pressure on lead, had to narrow lead impedance, and a feasible way to reduce lead impedance is shorten the distance of earth-sized distance with change, to reduce the lead impedance, lower pressure drop, lead so lightning arrester should be installed in a distribution transformer close point is more suitable.

 

2. It should also be installed on the side with low pressure.

If with low voltage side is not installed earth-sized, when high side lightning arrester discharge lightning current to the earth, the producing pressure drop on the grounding device, the pressure drop through the variable shell and neutral role in low voltage winding. Flows so low voltage winding of lightning current will make the high voltage winding according to than high induction electric potential (up to 1000 kV), the potential will be the superposition of the ray voltage and high voltage winding neutral point potential rise, causing high side winding insulation breakdown near neutral point. If installed on the low voltage side of earth-sized, when make the grounding device of high voltage side earth-sized discharge potential rise to a certain value, the low voltage side earth-sized began to discharge, make the low voltage winding wire end instead of neutral point and the shell of the potential difference is reduced, so that it can eliminate or reduce the influence of "inversion" potential.

 

3. The MOA grounding line shall be connected to the matching shell.

The grounding line of MOA shall be connected directly to the distribution transformer housing, and then the enclosure shall be connected with the earth. It is wrong to connect the ground wire of the arrester directly to the earth, and then to connect the ground wire to the transformer shell from the ground pile. In addition, the grounding line of the arrester should be reduced as far as possible to reduce the residual pressure.

 

4. Regular maintenance tests are required in strict accordance with the procedures.

The insulation resistance measurement and leakage current testing of MOA is conducted regularly. Once the MOA insulation resistance is found to be significantly reduced or puncture, it should be replaced immediately to ensure the safe and healthy operation.


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