The discovery of the non-linear properties of silicon carbide (SiC) around 1930 made
feasible the introduction of valve-type surge arresters to protect power systems against
atmospheric discharges. The general design of a conventional arrester consists of
plate-type gaps spaced by insulating rings with series non-linear SiC resistors also
known as thyrite. The spark gap performs the switching function and the SiC resistor
limits the follow current and enables the arrester to reseal. By subdividing the spark
gap, it is possible to reseal at higher voltages eliminating steady state energy dissipation.
Compared with spark gaps, valve-type arresters have a number of advantages
but the protective level remains relatively high. The SiC elements have severe specification
standards because most of the voltage is supported by the non-linear resistors
and the arc voltage is comparatively negligible; also most of the energy associated
with the discharge of a transmission line/cable is absorbed by the SiC non-linear
resistors.