Composite arrester

MOA (MOA) during normal operation and distribution transformers in parallel, the terminating line, the lower end of the ground. When the line when an overvoltage occurs, then the distribution transformer will withstand over three parts dropout voltage generated through the arrester, wire and grounding device, called the residual pressure. In this three-part overvoltage, the metal oxide arrester residual voltage on its own performance related to its residual voltage value is constant. Residual voltage on the grounding device can be connected to the grounding deflectors distribution transformer housing, then connected to the grounding device and means to eliminate them. And how to reduce the residual voltage of the leads has become the key to the protection of distribution transformers. Leads through the current frequency impedance, varistors the higher the frequency, the stronger the wire inductance, impedance increases. Seen from U = IR, to reduce the residual pressure on the lead, you have to narrow the lead impedance, and possible ways to reduce the lead impedance is to shorten the distance between Composite arrester from distribution transformer to reduce the lead impedance, lower lead drop, so arresters should be installed in a more appropriate distribution transformer near point distance.

Metal oxide varistors

Mov varistor valve main ingredient is zinc oxide, zinc oxide varistor has a very excellent nonlinear characteristics. Under normal operating voltage of the resistance value is very high, in fact, the equivalent of an insulator, and in the over-voltage is applied, the resistance of the resistive sheet is small, residual pressure is very low. But under normal operating voltage, since the valve sheet to withstand long-term effect of power frequency voltage generated by the degradation caused by changes in resistance characteristics, resulting in increased flow through the valve leakage current. The resistive component of the current sharp increase in temperature will rise valves on thermal crashes, serious, mov metal oxide varistor or even cause explosion arrester. In accordance with the provisions of rules 1, MOA total of six test items, namely (1) Composite arrester Insulation resistance (2) Leakage Current DC U1mA and 0.75U1mA under (3) AC operating voltage under leakage current (4) Power frequency Power frequency reference voltage (5) Base insulation resistance (6) Check discharge counter action case reference current.