7. Choice of surge arresters

The choice of protective device, spark gap or lightning arrester, can be made on the basis of the following criteria:

• economical, as the spark gap is less expensive than the surge arrester;

• technique, as the spark gap causes an interruption in service and presents a wide dispersion of firing conditions (thus providing less effective protection).

Then it all depends on the type of network and the insulation level of the various equipment to be protected.

The problem of choosing between a silicon carbide arrester with spark gaps or a zinc oxide arrester hardly arises at all, since zinc oxide arresters have rapidly replaced their silicon carbide counterparts with spark gaps, especially for high...