When people think of lightning arresters, they often picture a simple, tube-like device. In reality, to accommodate various voltage levels and environmental requirements, these devices are generally classified into three categories: silicon carbide (SiC) arresters (an older type), metal-oxide arresters (the current mainstream), and composite-housed arresters (a newer design). Understanding the differences between these types is the first step in selecting the right equipment.

I. Traditional Silicon Carbide (SiC) Arresters: Simple in Principle, High in Maintenance

The first category consists of silicon carbide (SiC) arresters - the "veterans" of power systems. Their core operating principle involves a spark gap placed in parallel with silicon carbide valve elements. When a lightning surge occurs, the spark gap breaks down and discharges, shunting the overvoltage to the ground before returning to an insulating state.

While these arresters feature a simple structure and high surge-withstanding capability, they have two significant drawbacks: relatively poor protective characteristics (resulting in higher residual voltage) and a bulky design. Furthermore, the spark gaps require regular maintenance to prevent malfunctions - such as failing to trigger when needed or triggering erroneously. They are rarely used in new projects today, appearing mostly in retrofit or replacement scenarios at older substations.

II. Metal-Oxide Arresters (MOA): The Mainstream Choice for Gapless Protection

The second category - and currently the most widely used - is the metal-oxide arrester (MOA). These devices eliminate the series spark gap entirely, relying instead on the non-linear voltage-current characteristics of zinc-oxide valve elements. Under normal operating voltage, the arrester exhibits high resistance, allowing virtually no current to pass. When the voltage exceeds a specific threshold, the resistance drops instantaneously, rapidly shunting the lightning current to the ground.

A key criterion for evaluating the condition of these arresters is "leakage current monitoring." In practice, technicians focus on the resistive component of the total leakage current; a significant increase in this resistive current often indicates that the valve elements have become damp or aged. Because they lack a spark gap, these arresters offer extremely fast response times and superior protective performance compared to traditional types, making them the preferred choice for medium- and high-voltage power grids.

III. Composite-Housed Surge Arresters: A Practical Choice for Lightweight Design and Pollution-Flashover Resistance

The third category consists of composite-housed surge arresters, which represent an innovation in materials. While their internal core typically still utilizes metal-oxide valve elements, the traditional porcelain housing has been replaced by an exterior enclosure made of silicone rubber composite material.

This advancement offers significant advantages: the units are lightweight, facilitating easier installation and transport. More importantly, the silicone rubber sheds - or "skirts" - possess excellent hydrophobicity and self-cleaning properties, effectively preventing surface flashover incidents in environments characterized by high humidity, dust, or coastal salt spray. When selecting these arresters, it is crucial to verify the UV-aging resistance of the composite housing to ensure that it will not chalk or crack during long-term outdoor operation.