Okonite wire and cable - Short Circuit Currents / Conductor Currents
Short Circuit Currents
Conductor Currents

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With the ever-increasing kva capacity of power systems, the possible short circuit currents are becoming so high that it is frequently necessary to consider the effect of these short circuits on the heating of the cables. The conductor size must be large enough to carry the short circuit current for a sufficient length of time to permit the circuit breakers to open before the conductor is heated to the point where it damages the insulation.

The chart at right shows the maximum currents to which various size copper conductors can be subjected for various times without injuring the insulation. It is based on a 90C conductor operating temperature. The maximum current for short circuit ratings for 75C conductor temperatures and for other than 250C may be obtained by multiplying the value obtained for T1 = 90C and T2 = 250C from chart by appropriate correction factor for other values of T1 and T2.

 

Allowable short circuit currents
for insulated copper conductors*

short circuit currents
 
 

COPPER & ALUMINUM CORRECTION
FACTORS FOR VARIOUS
SHORT CIRCUIT TEMPERATURES
Short Circuit Temp. (T2)

 

175C

200C

225C

250C

T1 = 75C

.84

.92

.99

1.06

T1 = 90C

.76

.85

.93

1.00

 


ENGINEERING TECHNICAL CENTER

Every effort has been made to ensure the accuracy of this presentation.
However, information is subject to change. Not responsible for typographical errors.

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102 Hilltop Road
Ramsey, New Jersey 07446
Phone 201-825-0300
Fax 201-825-3524
info@okonite.com

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