In a static over-current relay, inverse time characteristics are obtained by

The correct answer is 'option 2'

Solution:

The inverse time circuit breakers are associated with a thermal characteristic. At lower over current levels, the circuit breaker must wait for some time to see if this temporary fault. After letting the overcurrent flow for some time, if it is still experiencing some fault current then the interrupting circuit breaker must break the circuit. This is called the inverse time characteristic.

• In static relays, it is advantageous to choose a circuit accommodating a wide range of alternative inverse time characteristics, precise minimum operating levels, definite minimum times, and additional high set features, if necessary.
• The relay is designed with integrated circuits to have adjustable slope characteristics to have versatile application in the modern complex power systems to match with those of the system components like fuses, transmission lines, and motors.

The inverse time characteristics of a relay are given below