The paper presents an analysis of overvoltages caused by a direct lightning strike in intrusion detection system equipped with underground radiating cable sensors. Waveforms of currents and voltages in the system components are calculated using analytical formulas basing on a transmission-line model in the frequency domain. The time-domain waveforms are computed using the inverse fast Fourier transform (IFFT). Three network configurations of the intrusion detection system are analyzed.

Electric arc is a complex phenomenon occurring during the current interruption process in the power system. Therefore performing digital simulations is often necessary to analyse transient conditions in power system during switching operations. This paper deals with the electric arc modelling and its implementation in simulation software for transient analyses during switching conditions in power system. Cassie, Cassie-Mayr as well as Schwarz-Avdonin equations describing the behaviour of the electric arc during the current interruption process have been implemented in EMTP-ATP simulation software and presented in this paper. The models developed have been used for transient simulations to analyse impact of the particular model and its parameters on Transient Recovery Voltage in different switching scenarios: during shunt reactor switching-off as well as during capacitor bank current switching-off. The selected simulation cases represent typical practical scenarios for inductive and capacitive currents breaking, respectively.

The effectiveness of lightning protection on the power and distribution grid is a significant factor, which influences the power distribution reliability and the failure rate of system elements. As part of this article, a mathematical model will be presented, taking into account selected parameters that affect the assessment of the lightning hazard of an overhead line. The proposed model will consider the location of the object near the line and the adjustment of line conductor overhangs. Moreover, the mentioned mathematical model allows for analyzing the impact of considered parameters on the protection level of the power system, and transient overvoltages that occur in this system. The article contains also a detailed description of an effective and fast method to assess the lightning discharge impact on the power system with insufficient data. The introduced model was tested to verify the correctness of its operation by comparison of calculation results and functional data. High convergence of calculated and functional data and uncomplicated model structure ensure a wide range of applications for the proposed solution to easily prevent emergency situations in the power system. Furthermore, the described model gives the opportunity to assess the reduction of the range of selectivity zone associated with the power line, in conjunction with the impact of constructional peculiarities and a near object.

The purpose of this research work is to study the issues of the protection of 6–10 kV lines and access ways overvoltage in the electrical networks of modern enterprises of high-energy intensity, as well as the search for real technical opportunities to improve the protection of power lines directly in conditions of their operation. The methodology of this scientific research is based on a combination of methods of system analysis of the principles of the functioning of electric networks of energy-intensive enterprises with an analytical study of the fundamental aspects of ensuring the protection of 6 to 10 kV lines and access ways from overvoltage. The results of the conducted scientific research indicate the relevance of the issues of ensuring the protection of lines and electrical networks of energy-intensive enterprises from overvoltage and the need to develop special technical devices to ensure the proper level of such protection in real conditions. The results and conclusions of this research work are of significant importance for developers and designers of electric networks of enterprises with increased energy capacity, as well as for employees of various power supply systems who, by their occupation, face the tasks of servicing electric networks, which include lines and access ways with specified operating voltage parameters and ensuring the proper level of safety and practical use of these electric networks of energy-intensive enterprises.