Voltage slow variations and harmonics analysis in a LV distribution point

Both suppliers and end-users are more interested in knowing the power quality (PQ) level through their common network. Unfortunately, there are no clear experimental methods and especially interpretable for all PQ aspects. This is also the case of the slow voltage variations about which it is theoretically known that they include variations with periods between (5 min+24 h), so practically the voltage wave will be decomposed in harmonics, being considered those which are in the mentioned range and then the statistical indicators will be determined. The paper aims to analyze the experimental voltage waves, but applying a new principle, that is the decomposition of the voltage wave firstly in step type actions and secondly in harmonics. The step type actions may resulting after the switching power transformers or autotransformers plots, change of electrical networks configurations, commutation of capacitor banks steps or after some jumps recorded by electrical power consumption. Beside the voltage variations analysis it was considered useful the voltage wave harmonic analysis in order to report some possible operating modes located outside of admissible limits. Overall, this paper represents a case study and also an analysis guide for slow voltage variations.