HOW DOES DIFFERENTIAL RELAY IS USEFUL FOR TRANSMISSION LINE


#1

HOW DOES DIFFERENTIAL RELAY IS USEFUL FOR TRANSMISSION LINE

Differential relay measures the difference between input and output currents of the protected equipment differential relays are used for the protection of transformers, generators it is very sensitive to the faults that occur in the protected region but they are less sensitive to the faults that occur outside the protected region the operation of the differential relay is different from other relays it operates depends upon the difference between two or more electrical qualities which means it operates depends on the phase difference of two or more electrical qualities
This relay is used to checks the difference between the input and output currents for the power system, and the difference will be normally like the magnitude or in phase angle for the proper operation this variation must be ‘zero’

REQUIRED FEATURES FOR THE WORKING OF DIFFERENTIAL RELAY

• It should have two or more similar quantities
• The electrical quantities should have the phase displacement of nearly 180 degree

TYPES OF DIFFERENTIAL RELAY

• Current differential relay
• Voltage balance differential relay
• Biased differential relay

CURRENT DIFFERENTIAL RELAY

This type of relay operates when there is a phase difference between current entering the electrical system and the leaving current from the system

image

VOLTAGE BALANCE DIFFERENTIAL RELAY

We can’t use a current differential relay for the protection of the feeder in order to do that we need to use voltage differential relay

BIASED DIFFERENTIAL RELAY

image

This type of relay is the same as a current relay but it is connected in a differential circuit and an additional restraining coil is connected to pilot wires