Classification of Relays

 Classification of Relays

Classification or the types of relays depend on the function for which they are used. 

Some of the categories include protective, reclosing, regulating, auxiliary and monitoring relays.

Protective relays continuously monitor these parameters: voltage, current, and power; and, if these parameters violate from the set limits, the protective relays generate an alarm or isolate that particular circuit. 

These types of relays are used to protect

equipments like motors, generators, and transformers, and so on. 

Some of these are induction type over current relays, distance relays, differential relays, etc.

Reclosing relays are used to connect various components and devices within the system network, such as synchronizing process, and to restore various devices soon after any electrical fault vanishes, and also to connect transformers and feeders to a line network.

Regulating relays are the switches that contact such that a voltage boosts up as in the case of tap-changing transformers.

Auxiliary contacts are used, in circuit breakers and other protective equipments for contact multiplication. 

Monitoring relays monitor a system conditions such as direction of power and accordingly generates an alarm. 

These relays are also called as directional relays.

Depending on the operating principle and structural features, relays are of different types.

Electromagnetic relays, thermal relays, power varied relays, multi-dimensional

relays, and so on, with varied ratings, sizes and applications.