Lightning arrester: Why can it withstand lightning strikes? How does it work? What are the types of lightning arresters? Next, please follow me to explore the mystery of the lightning arrester and understand the "family history" behind it.
Metal oxide arrester, an overvoltage protection device, is famous for its excellent protection performance, lightweight quality, pollution resistance and stable performance. It cleverly utilizes the nonlinear volt-ampere characteristics of zinc oxide to ensure that under normal operating voltage, the current in the arrester is minimal (only microamps or milliamperes). However, once overvoltage occurs, its resistance will decrease rapidly, thereby effectively releasing the energy of the overvoltage and achieving protection. It is worth mentioning that this arrester abandons the discharge gap design of traditional valve arresters and relies entirely on the nonlinear characteristics of zinc oxide to complete the tasks of draining and breaking.
Next, let’s take a closer look at how metal oxide surge arresters work.
Since its advent in the 1970s, this lightning arrester has occupied a place in the field of lightning protection with its unique working mechanism. Its core component is a zinc oxide varistor. Each varistor is given a specific switching voltage, that is, the varistor voltage, when it is manufactured. Under normal operating voltage, these varistors present a high-resistance state, equivalent to insulators; however, when encountering a surge voltage, the resistance of the varistors will drop sharply and be broken down, thus presenting a short-circuit state. It is worth noting that this breakdown state is not permanent damage. Once the voltage higher than the varistor voltage is removed, the varistor can return to its high resistance state. Therefore, after installing a zinc oxide arrester on a power line, once a lightning strike occurs, the high voltage of the lightning wave will breakdown the varistor, causing the lightning current to flow into the earth through the varistor, thereby effectively controlling the voltage on the power line within a safe range and ensuring the safety of electrical equipment. According to the place of operation and use, arresters can be divided into the following categories:For AC systems, arresters are mainly divided into power station type, distribution type, parallel compensation capacitor bank protection type, electrified railway type, etc. In addition, there are special types for motors and motor neutral points, transformer neutral point types, gas-insulated metal-enclosed arresters and line-type suspended arresters. In DC systems, there are also many types of arresters. They include valve hall arresters, DC field arresters, DC filter-specific arresters, DC circuit breaker supporting arresters and subway-specific DC arresters, etc.
