TABLE OF CONTENTS The evolution of surge arrester technology has been characterised by both the gradual improvement of the various arrester components, and more importantly by four successive major steps: the simple spark gap, the valve-type arrester, the introduction of active gaps and the gapless metal oxide arrester. The latter is associated with ZnO varistors, and the two former arresters were made with SiC resistors. The introduction of each arrester had an important impact on protection levels and cost of the power system equipment as a whole.
During the first half of the twentieth century, protection of apparatus in electrical power systems was provided by rod gaps (also referred to as coordinating gaps) and a very high withstand voltage for the insulation [1].
The advantage of rod gaps lies in their simplicity and cost. However, they cannot support any voltage during their operation and cannot clear the power frequency follow current, which means that after sparking over, a permanent fault occurs which leads to interruption of supply. Moreover, the time lag to sparkover and the dependence of sparkover on many factors may result in failure of the protective system. The combination of a high protective level with spark gaps still finds application today in low voltage applications, but at high service voltages increasing the withstand voltage of insulation has a marked influence on costs.
At 33 kV systems and lower, it is not recommended to use simple rod gaps because they may be...
