Metal Oxide Arrester (MOA) is a new type of lightning arrester developed in the 1970s. It mainly uses zinc oxide (ZnO) as the main material and utilizes its excellent nonlinear volt ampere characteristics to achieve overvoltage protection for power systems.

1、Working principle

The zinc oxide lightning arrester is mainly composed of zinc oxide valve plates (ZnO resistor plates) connected in series or parallel. Its core working principle is based on the nonlinear resistance characteristics of zinc oxide material:

Under normal operating voltage: The zinc oxide valve plate presents a high impedance state, with only microampere leakage current passing through, equivalent to an insulator, which does not affect the normal operation of the system.

When overvoltage occurs: When the system voltage exceeds a certain threshold (such as lightning overvoltage or operation overvoltage), the zinc oxide valve plate quickly transitions to a low impedance state, releasing the overvoltage energy into the ground through the valve plate, thereby limiting the voltage amplitude on the equipment.

After the overvoltage disappears, the valve automatically returns to a high impedance state, and the system resumes normal operation.

2、Structural composition

Zinc oxide lightning arrester usually consists of the following parts:

Zinc oxide valve plate: a core component with excellent nonlinear resistance characteristics.

Insulated jacket: usually made of silicone rubber or ceramic material, providing electrical insulation and mechanical protection.

Metal terminals: used for connecting with power systems.

Pressure relief device: releases pressure in case of internal malfunction to prevent explosion.

Sealing structure: Ensure that the valve disc is not affected by external environmental factors such as moisture and dust.

3、Main features

Excellent nonlinear characteristics: The resistance of zinc oxide valve plates varies nonlinearly with voltage, with extremely high resistance under normal voltage and a sharp decrease in resistance during overvoltage, resulting in a fast response speed.

Gap free design: Unlike traditional silicon carbide lightning arresters, zinc oxide lightning arresters do not require discharge gaps, have a simpler structure, and higher reliability.

Large current capacity: able to withstand large lightning impulse currents and operating overvoltages.

Residual voltage: Under the same rated voltage, the residual voltage (protection level) of zinc oxide lightning arrester is lower than that of traditional lightning arrester, and the protection effect is better.

Low freewheeling: After the overvoltage disappears, the valve plate quickly recovers high impedance without freewheeling phenomenon, reducing energy loss.

Good sealing performance: adopting a sealing structure to prevent the valve plate from getting damp and aging, extending its service life.

Easy to maintain: With a simple structure, there is no need for frequent maintenance, reducing maintenance costs.

4、Application Fields

Zinc oxide lightning arresters are widely used in various fields of power systems, including:

Power plants and substations: protect important electrical equipment such as transformers and switchgear.

Transmission lines: prevent lightning waves from entering and protect the insulation of the lines.

Power distribution system: protects equipment such as distribution transformers and cables.

Industrial and civil buildings: protect electrical equipment from damage caused by lightning and operational overvoltage.

Railway and rail transit: protect signal systems, traction substations and other equipment.