In most cases, failures of electrical and electronic equipment caused by overvoltage and / or load changes in the lines of supply. The main reason for the high sensitivity of modern electrical equipment to electromagnetic disturbances caused by the use of integrated semiconductor devices of high dimensionality. The most common source of surge is lightning. It's an unpredictable natural phenomenon of high intensity can cause overvoltage surges transmitted through air supply line, a distance of up to several kilometers from the lightning strike. Spreading of the lightning current along the surface of the earth can cause impulse voltage in cable networks, electric power. In addition to the pulse caused by lightning, surges in the electricity network can be caused by turning on and off of inductive loads (eg motors) or capacitive loads (capacitors for power factor correction) etc. To protect equipment and users, at the entrance of the active power equipment necessary to provide special security devices. These devices divert surges in power lines from the sensitive electrical equipment on the ground.
Currently on the market to achieve the required high level of protection uses the following technologies: Spark gaps. Spark gap – Unheated gas-filled device, dramatically changing its electrical conductivity when a discharge between the electrodes. His used as a rapid switch in communication devices, locations, nuclear and experimental physics, etc. The design gap is simple: in a glass or ceramic container filled with gas, there are 2 or more electrodes from refractory metals or their alloys. For the filling used inert gases and their mixtures, hydrogen, nitrogen, oxygen, air, water vapor.