Example of application of factors ku and ks

An example in the estimation of actual maximum kVA demands at all levels of an installation, from each load position to the point of supply is given Fig. A14.

In this example, the total installed apparent power is 126.6 kVA, which corresponds to an actual (estimated) maximum value at the LV terminals of the MV/LV transformer of 65 kVA only.

Note: in order to select cable sizes for the distribution circuits of an installation, the current I (in amps) through a circuit is determined from the equation:

[math]\displaystyle{ \mbox{I}=\frac{\mbox{kVA}\times10^3}{\mbox{U}\sqrt3} }[/math]

where kVA is the actual maximum 3-phase apparent-power value shown on the diagram for the circuit concerned, and U is the phase to- phase voltage (in volts).

(click on the image to view it in larger size)

Fig. A14 – An example in estimating the maximum predicted loading of an installation (the factor values used are for demonstration purposes only)