What are the purpose of relay in the electrical system?

-Relay used to make isolation in two different circuits with different properties .

-Relays are switches that open and close circuits electromechanically or electronically. Relays control one electrical circuit by opening and closing contacts in another circuit. As relay diagrams show, when a relay contact is normally open (NO), there is an open contact when the relay is not energized. When a relay contact is Normally Closed (NC), there is a closed contact when the relay is not energized.

 

 

(1) Relay is a device which has become an essential component in the today's technology.

(2) Depending upon the Type of Application, relays are selected.

(3) The Purpose of relay in Electrical system as follow below: 

Relays are utilized to protect electric power systems against trouble and power blackouts as well as to regulate and control the generation and distribution of power

it is used mainly for switching

relay is a device which senses the fault and sends the signal to the circuit breaker before the equipment gets damage.

A relay is an electrically operated switch. Many relays use an electromagnet to mechanically operate a switch, but other operating principles are also used, such as solid-state relays. Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal. The first relays were used in long distance telegraph circuits as amplifiers: they repeated the signal coming in from one circuit and re-transmitted it on another circuit. Relays were used extensively in telephone exchanges and early computers to perform logical operations. A type of relay that can handle the high power required to directly control an electric motor or other loads is called a contactor. Solid-state relays control power circuits with no moving parts, instead using a semiconductor device to perform switching. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults; in modern electric power systems these functions are performed by digital instruments still called "protective relays".

 

HI

 

Basically, relay is a electrically operated switch. It is not device. it is used for isolation of the control circuit .Many relays use an electromagnet to mechanically operate a switch, but other operating principle are same

 

In modern machines Relays are operated by control voltage of the system (normally low volt DC) and switch on/off the power supplied (normally high volt AC) to other devices in the system.

There are various other used as well, I just mentioned one which I find most common. 

When you use a relay, you keep current portion of the circuit away from the switch and pulls the current directly from the battery to your KC's. The relay also allows you to tie your lights into a secondary12-volt circuit such as your high/low beams or ignition.

safety of Electrical instruments

Relay s.provide isolation in power circuit . Realys are often used with CTs and PTs or VTs which are used for protection,Relays are switches that open and close circuits electromechanically or electronically. Relays control one electrical circuit by opening and closing contacts in another circuit.

relay sensing element actuates the circuit breaker in abnormal current flow condition.