The basic working principle of metal oxide surge arresters is a zinc oxide valve disc sealed in a porcelain sleeve. The zinc oxide valve is based on ZnO as a matrix, and a small amount of  Bi2O3、MnO2、Sb2O3、Co3O3、Cr2O3 non-linear resistors are added.

It has much better nonlinear volt-ampere characteristics than silicon carbide, and only a micro-ampere leakage current flows under continuous working voltage , No continuous flow after the action. Therefore, the metal zinc oxide arrester does not require a spark gap, which simplifies the structure, and has the advantages of fast action response, resistance to multiple lightning overvoltages or operating overvoltages, large energy absorption capacity, and good pollution resistance. Since the protection performance of metal zinc oxide surge arresters is better than that of silicon carbide surge arresters, they have gradually replaced silicon carbide surge arresters and are widely used in AC and DC systems to protect the insulation of power generation and transformation equipment, especially suitable for effective neutral grounding (see power systems The grid of 110 kV and above with neutral point grounding method).