The paper presents the results of experimental registrations and numerical simulations of the transient overvoltages caused by single phase intermittent arc earth fault in 35 kV network with isolated neutral. Experimental laboratory investigation is performed in order to implement appropriate arc fault model for arcs with low and discontinuous current. Single phase to earth arc fault is created in field in 35 kV network. Numerical model of the system is created in EMTP-ATP software. Overvoltage waveshapes and overvoltage factors are calculated and compared to measured values. Good agreement between the measured and calculated results is achieved.

This paper deals with applying the sliding Fast Fourier Transform analysis to detect voltage dips and swells in modern distribution networks. Significant odd and even voltage harmonics appear during voltage dips and swells, and they can be used to detect these events. Since the voltage waveshape during the dips and swells have the same harmonic content, the separation of these events can be done by calculating the angles of the voltage harmonics at the moment of the event. In the case of voltage swells phase angles of the 1 ^st and the higher order harmonics have the same polarity, while in the case of voltage dips phase angles of the 1 ^st and of the higher order harmonics have the opposite polarity. The presented approach is verified by analyzing mathematical signals and signals measured in real distribution networks with renewable sources. The limitation of the analyzed method is that the amplitude of voltage variation during the dip or swell in a real distribution network cannot be reliably associated with the calculated values of voltage harmonics. This limitation can be overcome by considering the value of 1 ^st voltage harmonic, or RMS voltage value calculated for one cycle or half cycle of the voltage wave.

This paper analyses and compares the conventional lightning protection systems proposed in IEC 62305 to the lightning protection systems based on the application of early streamer emission lightning rods proposed in NF C 17-102. Comparison between the two approaches to the lightning protection of structures was presented, both from a technical and economic point of view. Some inconsistencies in the conventional air termination system design methods are pointed out. The critical attitude of the scientific community regarding the declared protection characteristics of the early streamer emission lightning rods is discussed.

This paper presents a power quality analysis of a 50 MW photovoltaic (PV) power plant connected to a 220 kV overhead transmission line in a Southeast European country. The analysis covers a seven-day measurement period. Voltage quality is assessed in accordance with the requirements of the grid codes of three transmission system operators (TSOs) in Southeast Europe. In contrast, current quality was evaluated following the IEEE Std. 2800. The results show that PV power plants, as nonlinear sources of electrical energy, slightly influence power quality parameters, particularly through the generation of harmonics. Continuous monitoring of power quality parameters is important to ensure compliance with relevant technical documents, especially in the case of wide-scale integration of PV and wind power plants into the power system.