Calculation need helps

[sparki2010]

1. A 630 kVA transformer feeds a 3phase 400 V 50 Hz main switchboard located at distance of 100m and is connected using 2 parallel runs of 240 sq.mm 4 core copper cable buried underground. An arc fault takes place on the bus terminals while an operator is trying to do live work in a panel (with the cover of a breaker open). Calculate the incident thermal energy on the operator and the PPE class necessary to be used based on IEEE formulae given in the course notes:
Box type configuration and bus gap of 40 mm can be assumed for the calculation. The working distance can be taken as 450 mm from the arc source.

Other data required for the calculation are as follows:
Transformer impedance 5% with X/R ratio 20
Cable impedance per km for each cable: R: 0.096 ohm and X: 0.077 Ohm
Tripping time of main LV circuit breaker clearing the bus fault is 0.4 second due to an intentionally introduced coordination delay.

Procedure:
 Evaluate the per unit resistance and reactance of the transformer and cables
 Calculate the symmetrical bolted fault current using first principles and the data given
 Calculate the arc fault current
 Calculate the normalized incident energy
 Calculate the incident thermal energy for the given situation
 Convert to cal/cm2 from J/cm2 (J=0.239 calories)
 Choose PPE rating (from the table in the Powerpoints) just higher than the calculated value