Types of Releases

There are "Relays" and "Releases". Please do your homework by reading IEC standards for example.

One example: "Relays" give electrical signals to trip a "Shunt release" in a circuit breaker in the event of a fault. The shunt release is itself an electromagnetic one, which, on electrical power being applied to it, mechanically moves and de-latches the circuit breaker.

Hope it helps?

Relays simply detect/sense the E-faults when it reaches at set tripping level it releases the NC contacts to open the circuit. Generally there are different kinds of Elect. RELAYS...but the root word release has its meaning (To set free from confinement, restraint, or bondage, to free from something that binds, fastens, or holds back).

Read IEC Handbook can be a great help.

http://www.schneider-electric.us/products-services/products/relays-and-timers

Here is an extract from a standard which follows IEC:

However, 'relay' has many meanings. Can be an aux contactor, timer, sensing device, and varies from country to country.