Electricity + Control October 2016

EARTHING + LIGHTNING PROTECTION

OPINION

DB – Distribution Board MCR – Measurement, Control and Regulation SPD – Surge Protection Device

Abbreviations/Acronyms

Brief guide to the selection of lightning and surge protection

Tony Rayner, Phoenix Contact South Africa

A basic explanation of what to consider when selecting lightning and surge protection.

I have just finished reading an article about ‘lightning strikes and surges’. Even though I have been in the industry for many years, it was difficult to understand and rather boring. In this light, I have attempted to simplify surge and lightning protection dynamics, thereby, hopefully, making it easier for prospective users to make an informed choice when purchasing protection systems. To simplify my explanation I have divided Surges into two categories, namely Lightning strikes and Other Surges. Lightning strikes Around the world there is lightning activity, some areas minimal, others moderate, and others extreme. Where ever there is lightning activity, huge amounts of energy may be induced into electrical reticu- lation, causing, in many instances, catastrophic damage. To protect systems against this phenomenon, lightning protection is required. It is also important to know that lightning protection should always be used in conjunction with surge protection. Why do we need protection?

Other surges Surge (other) protection is another matter. In general surges are manmade and mostly generated by electrical switching operations. Examples of these (amongst many others) could be the starting of inductive loads or power failures. Obviously these transients are pre- sent 24/7 affecting electrical supplies. Therefore it goes without saying that surge (other) protection is an imperative. So, even if you are not situated in a lightning area, surge (other) protection is still necessary. These extremely fast voltage and current disturbances, including lightning, which I prefer to call transients, cause hundreds of millions of Rands worth of damage to equipment every year.

What do we use for protection? Protection is broken up into three categories, namely:

• Type 1 (Class I) – Coarse protection. These devices are used for protection against Lightning Transients. Normally situated in the primary mains supply DB (Distribution Board) and used in conjunction with Type 2 devices

October ‘16 Electricity+Control

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