I2t Thermal Withsand


The thermal withstand of a cable can be determined by comparing the maximum energy at the fault, with the maximum energy the cable can absorb.  The equation for this is:

I2tk2A2

I2t is proportional to the energy let-through of the protective device
       I - fault current, A
       t - fault duration, S

k2A2 is proportional to the energy withstand of the cable
        k - adiabatic constant
        A - cable cross-sectional area, mm2

To better understand the theory behind the above, please see The adiabatic equation.

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