The manuscript presents a model of partial discharge activity taking place in the protrusion defect inside the cable system. Through such approach COMSOL MPh provides the capacitance values obtained from the model of power cable containing defect, while conventional capacitive equivalent circuit built in MATLAB, uses these values in order to describe partial discharge activity. Having in mind that real protrusions represent non-regular shaped cavities whose analytical capacitance computation is very complex, use of COMSOL Mph facilitates capacitance computation and then provides convenient platform for the MATLAB capacitive circuit use for non-regular shaped cavities.

The aim of this paper is to analyze the lightning protection model of a photovoltaic power plant, which is of great importance, in order to guarantee the smooth work of the system and avoid errors and damage to the equipment. Atmospheric discharges affect the proper operation of photovoltaic sources and their installation, including sensitive equipment. Determining the need for lightning protection and assessing the success of risk analysis are the first steps to adopt appropriate lightning protection measures. The paper assesses surges due to lightning strikes and the required protection measures based on the results of risk analysis and protection costs. Also, external and internal lightning protection systems, selection of equipment characteristics, and earthing systems are discussed. The lightning protection model was analyzed using the SCIT (Shield) software, and the risk analysis was processed in the Sparkta software.

Abstract Line surge arresters are mainly used for transmission line lightning performance improvement. Calculation of energy stresses of lines surge arrester is of extreme importance for the selection of the arrester class. Energy stresses of transmission line surge arresters due to multicomponent lightning flashes are analysed in this paper. To obtain lightning data two approaches were used: direct measurements using instrumented towers and lightning location systems. Both lightning monitoring systems are described. Data obtained from lightning monitoring systems are compared and used in simulations. Detailed modelling procedure for a transient analysis of the transmission lines is also described. Multicomponent lightning flash and 110 kV transmission line were modelled using Electromagnetic Transient Program -Restructured Version (EMTP – RV). The arrester current shapes and arrester energy duties are presented in order to clearly show influence of lightning current parameters to arrester energy duty.

Lightning is the main cause of line outages on overhead distribution lines, especially for lines located in mountain areas and without line surge arresters installed along the line. This paper is dedicated to lightning outage performance of distribution line “Kotor – Lovćen” that operates in mountain Lovćen area. Shielding failure rate, shielding failure flashover rate and back flashover rate are calculated using Sigma Slp software. Lightning data collected by two advanced lightning activity monitoring systems are analyzed and used in number of simulations conducted for purposes of this paper.

Different types of transient phenomena are found in power systems. Switching transients in power systems have always been a matter of concern in insulation coordination studies. The reactors in power system are widely used elements which purpose is to provide stable power flow in normal conditions and to reduce dynamical and thermal stresses during short circuits and some other faults. Many shunt reactors are switched frequently, even daily. Shunt reactor switching imposes a unique and severe stress on the connected system and the circuit breaker. This paper presents study of overvoltages due to shunt reactor switching in 400 kV substation.

For measuring lightning strokes, it is necessary to select the appropriate sensor. The nominal sensor parameters (lightning current peak and frequency range) should be selected taking into account that the lightning current peak which strikes the tower top can be up to 400 kA. In addition, sensors should be able to store all the components in one flash. This paper presents the system of testing and sensor calibration.

This paper is dedicated to transient studies on wind turbine blade due to different types of lightning discharges. In order to select the appropriate lightning protection system, it is necessary to identify the parameters of lightning flash. Therefore, measured lightning flashes are presented and analyzed. Simulations have been conducted in EMTP - RV. In the case when lightning hits the blade of wind turbine transient voltage on tower top, voltages on tower footing resistance and on primary side of transformer are considered.

This paper describes a detailed transmission line model for a transient analysis. Line surge arrester energy sharing and importance of complete transmission line modelling is explained. Lightning channel impedance and tower footing resistance are important parameters that influence line surge arrester energy duty. Therefore, energy stresses of transmission line surge arresters due to different values of lightning channel impedance and nonuniform distribution of tower footing resistance are considered.

This paper describes method for lightning current waveform parameters estimation from direct current measurements on remote lightning monitoring system. Proposed signal enhancemed method is based on segmentational multi-step digital signal enhancement in time domain. Performance of proposed waveform parameter estimation has been confirmed in Monte Carlo simulation of three types of synthetic signals corrupted with different levels of additive Gaussian white noise. The proposed approach for noise reduction in time domain offers satisfactory results.

The paper presents the analytics of lightning data collected by monitoring system in real - time for the measurement of the direct lightning current (LAMS) and the lightning location system (LINET). The both systems and their operation mode are shortly described. A great number of collected data are analyzed, explained and compared. The data analyses showed the Lovćen mountain has the overall highest number of registered lightning strokes in the whole analyzed area.

Analysis of electric power system reliability presented in this paper, refers to complex (composite) systems. General issue of assessment of complex electric power system reliability is how to implement and solve mathematical system equivalents and their possible states, taking into account as many possible effects, impacts and conditions of their real functions. Number of possible states of the system in real conditions can be very big, so it is extremely difficult to explore all cases of assessing the reliability of such systems. In this paper, the methods of determining possible states of the system, as well as the methods of determining system deficit, are presented and analysed. For calculations of electric power system reliability, in order to carry out a complete analysis and calculation of characteristic system reliability parameters, it is necessary to determine deficit of electricity. The paper also presents the concrete results obtained using the developed mathematical model and software program developed on its basis.

Monitoring of lightning discharges has become an indispensable activity, in order to improve protection systems. To select the appropriate lightning protection systems, it is necessary to know the lightning current parameters: shape of lightning current (lightning current peak, duration of front), polarity, frequencies, number of components during the stroke. The systems for locating lightning discharges are today's modern tool for monitoring lightning discharges. To establish a better relation between the lightning current parameters, it is necessary to provide a significant number of statistical data, especially data which are obtained by measuring direct lightning current strokes. Thanks to the progress in developing measuring, information and communication technologies, today we have an opportunity for the development of new models and methods for measuring the parameters of the lightning current. This paper presents a system of links and characters that are used for the operation of the station for the direct measurement of of atmospheric discharges.

This paper introduces a new monitoring system in real-time for measurement of the direct lightning current. Its application on a broadcasting tower in Montenegro is described, and some field measurements are presented. For the selection of this monitoring location, a new approach was used, based on data provided by a Lightning Location System (LINET).

Lightning Activity Monitoring System (LAMS) provides very important data for transient analysis. This paper describes a new lightning activity monitoring system installed on the mountain Lovcen. First measurement data are shown and their importance in transient analysis due to direct lightning strokes on wind turbine blade is explained. This paper describes complete model for wind turbines testing under different lightning current shapes developed in EMTP - RV.