The normal MVA method, despite its simplicity, provides only an approximate solution to determine the fault levels in a power system. The final result in the normal MVA method does not provide the X/R value or power factor of the system.

The X/R ratio in a fault study enables the determination of asymmetrical fault current which is important in the selection of the momentary ratings of equipment. Using the normal MVA method, to get the value of the momentary current rating, multiply the symmetrical fault rating by 1.6 [1] for high voltage equipment. This value is typical and may not be applicable to every application.

The Complex MVA Method provides an easy way to determine the X/R values for a power system study.

The Complex MVA Method will be dealing with complex values but it will be much easier than using the Per Unit Method because no base transformation is necessary.

As we go further into the Complex MVA Method, we will be dealing with these common equations:

Next time, I will be presenting typical examples on the Complex MVA Method.

[1] IEEE C37.010

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