What is a relay?

What is a relay?

relay that detects the fault and the information given to the c.b. sequence of operation: relay-c.b-isolator:

Relays are switches that open and close circuits electromechanically or electronically. they control an electrical circuit by opening and closing contacts in another circuit. when a relay contact is normally open (no), there is an open contact when the relay is not energized.

it is a magnetic switch. it is a coil assembly connected to your circuit, a short circuit board with two terminals and an open terminal.

As soon as the direct current passes through the coil, it generates a constant magnetic field that attracts the plate and connects the open terminal to itself and disconnects from the closed terminal. then, it’s a simple magnetic switch.

a relay is a power switch.

Relays are used when it is necessary to control a circuit with a distinct low power signal or when multiple circuits must be controlled by a single signal.

It is usually used in protection system.relay trips the circuit breaker when the control variable (voltage, current or both) exceeds a preset value known as the relay start value.

A relay is a power switch. Many relays use an electromagnet to mechanically actuate a switch, but other operating principles are also used, such as solid-state relays. Relays are used when it is necessary to control a circuit by means of a low power signal (with complete electrical isolation between the control and controlled circuits), or when multiple circuits must be controlled by a single signal. the first relays were used as amplifiers in the long-distance telegraph circuits: they repeated the incoming signal of one circuit and retransmitted it on another circuit. relays have been widely used in telephone exchanges and early computers to perform logical operations.

According to the standards, a relay is defined as a set of switching contacts whose state is determined by the respect of certain predefined conditions.

we normally associate a relay with an electromagnetic switching device. it is only an example of a switching device whose state is determined by the presence of a voltage across a coil.

There are several relays without electromagnet. they include temperature sensitive thermostats, a pressure sensitive pressure switch, a current sensitive overload relay and many other types.


a relay is an electrical switch used to open or close a circuit with electromechanical relay or electronically.

it is usually used to switch a lower current.

it changes their states when the energies go from no (normally open) to close or from nc (normally closed) to open.

There are two types of electromechanical relay relays. In electromechanical relays, the contacts are opened or closed by a magnetic force.

solid state relays.with semiconductor relays (ssr), there are no contacts and switching is totally electronic.


did you hear about the relay race? The same is true for the relay being a sensing device that detects the circuit in real time and sends a trip command to the circuit breaker for operation.

but how ????

In fact, it takes an input current of 1 or 5 amps into the current transformers and a voltage input into the potential transformer. It now has a setpoint called the psm tap setting multiplier which is the limit value beyond this relay send trigger command and tsm, called the time setting multiplier. which allows a delay for the operation of the relay.

in the event of a fault 1 to 3 relay detection cycles if the delay allows it, or simply because of the load current, if the fault relay is sent immediately to the circuit breaker, the circuit breaker is now a mechanical device that puts about 40 to 60 ms to operate, after the fault is cleared, the total operating time is almost 100 ms, this time, the circuit must support the fault.

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