A modified simple algorithm for detection of voltage sags and swells in practical loads

This paper presents the implementation of a modified sliding window algorithm for the detection of sag and swell, by measuring RMS voltage updated every sample. The trigger obtained can be used in conjunction with the main control system of a Dynamic Voltage Restorer (DVR), or as a triggering function to a digital recorder or to a power line conditioner to detect the occurrence of sag and swell. The modeling of the algorithm and test of its functioning to variations in some of the parameters were carried out in a Matlab - Simulink environment. Reliability of the algorithm under conditions of noise and distortion in the input and to three different types of sags was tested on real data captured during events such as starting of induction motor, intermittent loading of welding transformer, and dynamic loading of a captive diesel generator.