What are Surge Arresters and Lightning Arresters? | Understand in 1 Minute

Surge Arresters and Lightning Arresters (also known as Metal Oxide Surge Arresters - MOSA or MOA) are the world's most advanced equipment for safeguarding lines and equipment against overvoltage damage caused by lightning and other factors.

Metal Oxide Arresters: Structure and Working Principle

Metal oxide arresters contain excellent non - linear zinc oxide varistors. During normal operation, they remain in a high - resistance state, with almost no current conduction. When an over - voltage hits the line, their resistance rapidly drops to a low - resistance state. This allows the large current generated by the over - voltage to be diverted into the ground. Once the over - voltage subsides, the arrester returns to its high - resistance state, thus protecting the lines and equipment.

The Distinct Differences between Lightning Rods and Surge Arresters | Lightning Arresters

Lightning Rod

A lightning rod is installed on the top of a building or equipment and is not connected to the line. When lightning strikes, the lightning receptor at its apex actively attracts the lightning. The lightning current generated is then safely transmitted to the grounding device via the down conductor beneath, and ultimately, the lightning current is diverted into the ground. This mechanism protects the building or equipment from direct lightning strikes.

Surge Arrester | Lightning Arresters

A surge arrester is connected in parallel between the line and the ground. It does not actively attract lightning. Only when an overvoltage occurs in the line does it start to conduct. It diverts the overvoltage current into the ground to protect the line and equipment. At this moment, a certain voltage remains across both ends of the arrester and on the line to ensure the normal operation of the equipment. This retained voltage, which is safe for both the equipment and the line, is called the residual voltage.