A novel approach toward interpretation and application of voltage unbalance factor

Voltage unbalance has been interpreted in a number of ways based on the conditions and complexities that are involved. This paper takes the widely used expression of voltage unbalance factor (VUF) and puts forward the various ambiguities that arise due to voltage variation and unbalance when applied to a test case. If the results are not properly interpreted, they affect decision making with regard to motor derating and protective system settings. It is also shown that various voltage combinations are possible for a particular VUF. By fixing an upper limit so as to signify the upper limit, a simple solution by way of conceptual interpretation is suggested to overcome the same. The discussion that is put forward is supported by a test case.