Delta Lightning Arrestors
WHY A DELTA SILICON ARRESTOR IS MORE EFFECTIVE
Conventional valve type arrestors are based on a 1935 patent. The basic design is a spark gap for the lightning to arc over, and a series resistor which is intended to limit the flow of follow current from the line.
For many years this was the best design on the market, but now there is something better. The DELTA silicon oxide varistor (SOV) arrestor offers a number of improvements over the 1935 design.
The basic design of the DELTA silicon oxide varistor (SOV) arrestor is a pair of metal electrodes separated by a silicon oxide compound. Under normal conditions, the silicon oxide is a good insulator so that no line current flows between the electrodes to ground. When an excessively high voltage occurs on the electrodes, the high energy electrical field ionizes the silicon oxide, changing it from a compound to silicon separate from oxygen. Since the silicon ion is a good conductor, the high energy current is conducted to ground. When the voltage falls toward normal, the silicon and oxygen recombine, forming silicon oxide and shutting off the conduction.
The reason the DELTA silicon oxide varistor (SOV) design works so much more effectively is that there is no series resistor to limit the flow of current. In valve arrestors, the resistor is there to limit the flow of the line current, but it also impedes the lightning discharge. Since the DELTA silicon oxide varistor (SOV) arrestor needs no resistor, it can conduct more current much faster.