New wavelet indexes for the severity assessment of transient disturbances on low-voltage distribution systems

Power Quality is a relatively new research area of power engineering. Its main purpose is the analysis, classification and correction of power disturbances.; There are many types of power disturbances. The two main types are: steady state disturbances (voltage distortion) and transient disturbances (impulses, sags, etc.). Sources for these disturbances can be found on both distribution and transmission networks.; The analysis and classification of these disturbances involves the application of several signal processing tools, most of them in the frequency domain. The most common is the Continuous Fourier Transform (CFT). This method is widely used for the study of steady state voltage distortion. It allows the decomposition of distorted waveforms into harmonic components and the calculation of distortion indexes. The use of CFT is limited to steady state disturbances because of its infinite time mathematical composition.; Transient disturbances are better analyzed using time domain methods. They are classified according to peak voltage, rise time, duration and energy content. Time domain methods are based on time differential equations and require large amounts of computer memory.; This study uses One Dimensional Wavelet Decomposition to develop wavelet distortion indexes to classify transient disturbances. The new wavelet distortion indexes will be similar to the harmonic distortion indexes used for steady state voltage distortion. Peak and one cycle RMS values of reconstructed signals from different wavelet scales will be combined to calculate the indexes. These indexes will relate to the CBEMA (Computer Business Equipment Manufacturers Association) Susceptibility Chart and they will provide an idea of the severity of the transient disturbances. The main contribution to the field is that a single number will provide sufficient information on the severity of a transient disturbance.; Wavelet decomposition is applied to a variety of transient disturbances. Real disturbances obtained from the field are used throughout this study. The results are compared to simulated disturbances for accuracy. The simulated disturbances are developed using IEEE test impulses. The decomposition plots of each disturbance are presented with their corresponding calculated indexes. The indexes are related to the severity of the disturbances and compared to the CBEMA tolerance.