My question is whether bellow formula is correct to find bus size for 46kA for 0.5 second & what is RT in bellow formula.
formula to calculate the size of busbar to withstand the thermal stresses due to currents with duration of 0.2 sec to 5 sec.
Sp = RT( I x I x t) / K
Where Sp – is the cross sectional area of bus bar in millimeters.
I - is the value of AC fault current.
t - is the operating time of disconnecting device in seconds.
K – is the factor depending on the material of the conductor, insulation and initial and final temperature.
Value of ‘k’ for copper is 143.
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