A fuzzy logic application to represent load sensitivity to voltage sags

This paper presents a case study application of fuzzy logic in a power quality issue. It describes the computer-based load sensitivity to voltage sags, by using fuzzy sets and IF-THEN inference rules. The load sensitivity is based on the steady-state and transient voltage versus time profile according to the IEEE Std. 446, also referred to as the CBEMA (Computer Based Equipment Manufacturer Association) curve. Fuzzy logic allows the modeling of the inherent uncertainty of the load reliability. This expresses how the success or failure of computer based loads is correlated with short term voltage variations in the electric supply system. A fuzzy inference system is experimentally implemented for these cases, showing the general procedures of how to use this theory. It appears that fuzzy set theory can play an important role in diagnosing power quality disturbances, and hence it can offer insights towards the satisfaction of the needs of manufacturers, utilities and customers