Surge arresters are electrical protective devices that are used to safeguard the transmission lines and terminal apparatus against the over voltage surges caused in the electrical circuit by the virtue of electrical switching operations and occurrence of natural lightening. The voltage surges, induced in an electrical power system due to lightning or switching operation, gives rise to the corresponding current surges; a surge is basically a sharp rise in the amplitude of a signal lasting for a very short time, this large current can cause insulation failure in the transmission and distribution line. This same current when flowing through the sensitive electronic devices at the power system terminal can cause damage to the devices.
The surge arresters are not designed to protect the power systems from a lightning strike, that task fall upon the lightening arresters. The main purpose of a surge arrester is to reduce and check the ill effects of the transients produced in the power system as a result of lightning strikes.
The classification of surge arresters can be done as follows:
Low voltage applications – These surge arresters find their applications in the low voltage power system protection applications, like protection of low voltage transformer or low rating motors.
Distribution level arresters – These surge arresters are employed at the distribution level of the power system; these are used to protect the distribution transformer, distribution cables and other distribution apparatus.
MV Surge Arresters – Also known as medium voltage surge arresters are employed in protection of substation apparatus working at medium voltages.
Common valve arresters at the station – These types of arresters are used to provide protection to 3~220KV transformer station apparatus and other equipment.
Magnetic blow arresters at the station – These arresters are used to protect 35~500KV transformer station apparatus and other equipment.
Magnetic blow valve arresters used in protection of rotating electric machines – The magnetic blow valve arresters are used to protect rotating electric machine like a synchronous generator and an induction motor against current as well as voltage harmonics.
Magnetic line blow arrester valve: These types of surge arresters are employed to provide surge protection to 330KV and above station apparatus and communication systems.
DC protection surge arresters – They are used for protection of insulation on the equipment and terminal apparatus working on DC system.
Arresters for neutral protection – These surge arresters have applications in Generator or motor neutral protection.
Fiber-tube surge arrester:These types of arresters find their main applications in protection of power system connecting wires.
Signal surge arresters, plug in type – These types of surge arresters find application in protection of twisted pair transmission line, the most common use of these arresters is to provide protection to high frequency feeders and communication systems like radio stations, mobile transmitting stations, high frequency receivers, etc.
Protection of coaxial cables – Coaxial cable plays a very important role in communication, especially in low loss long distance data transmission. The signal to noise ratio of a coaxial cable is much better than free space communication. It is thus very important to safeguard the coaxial cable. Special gas tube surge arresters are used to provide protection to coaxial cable against voltage and current surges.