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Surge current capacities

Supplier: Novaris
23 July, 2013

This document attempts to clarify the surge ratings of several Novaris power line and signal line surge protectors.

Surge rating1 is a specification that is often misunderstood. Most people would think that a surge protector rated at  200kA should be able to survive a 200kA surge. The largest surge current specified in both the British Standard BS6651 and the American Standard IEEE C62.41 is only 10kA. This figure has been reached through years of research and field measurements.

The largest surge current specified in any lightning protection standard anywhere in the world is only 70kA (Australian Standard AS1768). So, if lightning protection standards committees from around the world agree that a surge greater than 70kA will never occur, why are some surge protectors rated at 200kA? This is a straightforward question, and deserves an e qually straightforward answer.

The answer is that surge protectors rated at 200kA are not designed to withstand 200kA surges, but instead are designed withstand many surges of less than 70kA. To understand this concept an understanding of the surge protection components must first be gained.

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