According to metrological guidelines and specific legal requirements, every smart electronic electricity meter has to be constantly verified after pre-defined regular time intervals. The problem is that in most cases these pre-defined time intervals are based on some previous experience or empirical knowledge and rarely on scientifically sound data. Since the verification itself is a costly procedure it would be advantageous to put more effort into defining the required verification periods. Therefore, a fixed verification interval, recommended by various internal documents, standardised evaluation procedures and national legislation, could be technically and scientifically more justified and consequently more appropriate and trustworthy for the end user. This paper describes an experiment to determine the effect of alternating temperature and humidity and constant high current on a smart electronic electricity meter’s measurement accuracy. Based on an analysis of these effects it is proposed that the current fixed verification interval could be revised, taking into account also different climatic influence. The findings of this work could influence a new standardized procedure in respect of a meter’s verification interval.
The paper presents an FE model of coupled electromagnetic and thermal phenomena in Line Start Permanent Magnet Synchronous Motors (LSPMSMs). An algorithm for solving equations of a discrete model using the FEM has been presented. On the basis of this algorithm the author’s personally developed software for the analysis of coupled electromagnetic-thermal phenomena in the LSPMS motors was elaborated. This software was used to analyze the start-up process of motors with identical stator and rotor magnetic circuits and different materials of the starting cage. The start-up process of motors with the squirrel-cage made of aluminum and copper was considered. The influence of temperature on the start-up process has been taken into account. The results of simulation tests were compared with the results of measurements.