The following method of extrapolation should be used to calculate the losses of a transformer at 50% and 100%.

If a project is going to install a 800kVA transformer then in that case the calculation for 100% losses will be as following:

- Values prescribed by ECBC for transformer above and below the required one i.e. 800 kVA:

630kVA lower value losses at 100% 6.64

1000kVA upper value losses at 100% 9.80

- Difference of 370kVA and 3.16 losses at 100% loading

3.16/370=0.0085 (losses per kVA)

- Now subtract the installation transformer capacity with the lowest provided in ECBC that is 800-630=170kVA

170x0.0085= 1.44

- Finally, add the losses given in ECBC for 630kVA and 170kVA.

6.64+1.44=8.085kW is the maximum allowable power transformer loss for the mentioned transformer.