Study on consumers influence over the supplying network in a smart grid monitoring and state estimation

The paper analyzes the behavior of a three-phase consumer, consisting of several personal computers connected to a transformer´s secondary phases. The modalities of monitoring and recording of electrical quantities are presented in this work. The structure of the consumer is described. The recorded waveforms are analyzed. The Fast Fourier Transform (FFT) analysis allowed for the decomposition of the electric signals - voltages and currents - in harmonic components, which are presented both graphically and tabular. The quality indices are computed, underlining the capacitive nature of the consumer, firstly on each phase, then globally. There are presented some conclusions related to the variation of the electric quantities due to the load variation. In order to estimate the states, Discrete Wavelet Transform (DWT) is used. Some indices related to the power quality for the acquired signals have been determined and are presented in a tabular form. The analyzed consumer introduced strong distorted and non-symmetrical regimes, affecting the network. This is leading to the conclusion that some intelligent recording systems need to be designed and realized, in order to correctly estimate the different states in real time.