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Normal Inverse Curve Formula of BBC ICM Overcurrent Relay

Normal Inverse Curve Formula of BBC ICM Overcurrent Relay

Normal Inverse Curve Formula of BBC ICM Overcurrent Relay

(OP)
Hello everyone!

What is the formula of a Normal Inverse Curve of BBC ICM overcurrent relays?

Thanks.  

RE: Normal Inverse Curve Formula of BBC ICM Overcurrent Relay

There are different curves that can be set on certain circuit breakers with the equation for the curve defined by IEC 60255-151 (previosly  60255-3). This document is similar to IEEE C37.112 .

The equation is t = TMS(((k/((I/Is)^a) -1))+ C))))

Where:

t = operating time for a constant current

I = energising current

Is = overcurrent setting

TMS = time multiplying setting

k, a and c = constants defining the curve

For nor4mal Inverse, defined by the IEC, K = 0.14, a = 0.02 and c = 0.

RE: Normal Inverse Curve Formula of BBC ICM Overcurrent Relay

(OP)
Hello Juleselec & Sibeen,

Thanks for the information. The relay that im referring is the old one, the BBC ICM2.

Thanks very much.

GRAEE

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