What Is Trip Circuit Supervision Relay?

Protection System for Circuit Breakers, Trip Circuit Supervision of a Breaker, Supervision Relay for Circuit Breaker Trip circuit, Pre-Close Supervision of the Circuit Breaker and more about what is trip circuit supervision relay.. Get more data about what is trip circuit supervision relay.

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Protection System for Circuit Breakers

The protection system relies on the trip circuit. A trip circuit supervision relay is a watch dog for the trip circuit. If the trip circuit is not functioning, an alarm will be sent out.

A trip circuit should be ready to trip or disconnected. The protection system sends signal to the trip circuit. After receiving a signal trip circuit, it is possible to open or shut down a circuit breaker by means of actuating mechanical or electrical systems.

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Trip Circuit Supervision of a Breaker

A breaker has two trip coils. If relay issues a tripping command, the trip coil will go off. The breaker mechanism opens the circuit breaker when trip coil is electric.

If the trip coil healthiness is not monitored, the breaker may not open to clear the fault. The diagram of trip circuit supervision is shown in the figure. As the resistance of relay coil is less, a high resistance will be connected in series so that less current will flow through the circuit to operate the trip coil of the breaker.

Supervision Relay for Circuit Breaker Trip circuit

The use of separate DC supply for tripping is included in all the tripping schemes. A series tripping scheme is an alternative to using the fault current to trip the circuit breaker. Manual motor starters with thermal and magnetic trip features are called MPCBs.

The trip coil is shorted through the MPCB. The circuit breaker trips when the fault current goes through the trip coil after the MPCB blows off. The supervision relay type is intended for continuous supervision of circuit breaker trip circuit and gives an alarm for loss of auxiliary supply, faults on the trip coil or its wires.

The circuit breaker closed relays A and C are working. Relay A drops off and opens contact A1 to de-energize relay C if the trip circuit opens. Relay C is time delayed on drop-off by means of an RC circuit for a total time of 350 to 800 milliseconds, to prevent a false alarm due to a fault in other circuits or a normal tripping operation, when relay A is temporarily short-circuited.

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Pre-Close Supervision of the Circuit Breaker

The circuit breaker uses a trip coil to trip it during a fault condition. The trip circuit is an essential part of power system protection. The circuit consists of two relays Ra and Rb and they are connected.

The Qno and Qnc are the breaker status contact, which means that when the breaker is closed, the Qno becomes NC and the NC becomes NO. Pre close supervision means to sense the trip coil before the circuit breaker closes, and to check the healthiness of the trip coil during the open condition. It is called pre-close supervision.

If the trip coil is in an open circuit, the negative of the relay Ra and Rb will not be extended, since the NO of Ra and NC will be in Normal position. K1 and K2 are used for the post-closing and pre-closing schemes. The CB status contacts are 52 and 52b.

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Relay Life and Failure

When the primary relays are out of service, the backup relaying can be used. The larger part of the system is disconnected when the backup relay is on. If the primary relay fails, backup relays are tripped.

The life of a relay is determined by the life of its contacts. High in-rush currents, high sustained currents, and high voltage spikes are some of the causes of contact degradation. Poor contact alignment and open coils can cause relays to fail.

Motor control, automotive applications, electrical fuel pump, industrial applications, and so on are some of the typical applications of electromechanical relays. Relays are used to separate circuits. They are used for controlling multiple circuits.

They are also used to change over. Microprocessors use relays to control the load. Motor overload relays are used to protect the motor.