Classification of voltage sags in distribution systems due to short circuit faults

Voltage sags, one of the major power quality problems, are often caused by power systems faults. Many utilities have been trying to solve this problem but it still has not been any solution to prevent faults in power system. This paper presents a systematic and intuitive approach to analysis and classification of voltage sags, due to short-circuit faults in a 11kV distribution network. The symmetrical component classification is based on the decomposition of the three phase voltages. From positive and negative-sequence voltage a generalized magnitude for the event is defined. Generally, each type of voltage sag has different characteristics, i.e. magnitude and phase angle, and these characteristics are also different when the transformer winding connection is taken into consideration. The industrial 33/11 kV distribution network at Bajaj Hospital is taken as a case study. Simulation studies have been performed by using MATLAB/SIMULINK software.