Science, asked by amanjawaid770, 5 months ago

determine the time of operations of a 5 amp,3sec overcurrent relay having a current setting of1 25% and time multi0ler of 0.6 connected to the supply circuit through a 400/5 c.t when the ckt carries a foult current of 400A​

Answers

Answered by Anonymous
6

Answer:The pick up value of the relay is 5 amp but since the relay setting is 125%,

Operating current of the relay

= 5 × 1.25 = 6.25 Amp.

PSM =  

Secondary current

Relay current setting

=  

Primary current (fault current)

Relay current setting × CT ratio

=  

4000

= 8

6.25 × 80

From the standard 2.2 sec curve, the operating time for PSM = 8 is 3.2 sec.

Since the TMS is 0.6, the actual operating time of the relay is 1.92 sec.

Explanation:

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