A current relay is an integral part of electrical safety. Failure of an electrical system can endanger worker health and safety if it causes a machine or equipment to behave in an unsafe manner, or if the damaged system was operating as a hazard control. The processes necessary to repair a device that has been damaged by an undercurrent or overcurrent may also expose workers to additional hazards.
The current relay provides an effective method of equipment protection because its action depends entirely on the strength of the present it is monitoring. A classical current relay utilizes an electromagnet, which is activated by the presence of a certain amount of current flowing through the system it controls.
In instances where too much current flows through a piece of equipment, the electromagnetic field generated by the current will become sufficiently high in energizing the overcurrent relay. This will create the relay to switch on and do whatever function it was intended to carry out to prevent damage to the equipment. On the contrary, low current flow (undercurrent) through a circuit will result in a small electromagnetic field. This reduces the strength of the current relay’s electromagnet, causing the course to switch off, and in turn deactivating the part of the equipment endangered by the undercurrent.
Because relays work by reacting to the electromagnetic field generated by the system they monitor, they don’t need to be integrated into the specific circuit they're observing. For example, overcurrent relays are often used as a type of protective relay, and they function by tripping a circuit breaker once they are activated by the presence of current flows that are too high.