What is the function of an under voltage relay?

under voltage relay is used to protect the electrical equipment from the low voltage below the rated voltage till 80% of the network potential.

u/v relay is used to give a signal to emergency generator to start whenever the system voltage drops below (80%).

U/V relay number is (27) which is available in most electrical circuits to protect the following circuits by insulating them whenever the low voltage occurs:

LV/MV switch boards.

Motor feeders

Generator Circuits

Transformer circuits

u/v relay is considered to be one of the main protective relays in electrical design.