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The frequency‐dependent characteristics of the impedance parameter and the admittance parameter in the transmission line model of the transformer windings (TWs) are mainly result of the skin effect of the conductor and the complex permittivity's variation with the frequency of oil‐paper, respectively. In this study, an accurate fractional transmission line model of TWs considering the frequency‐dependent parameters is proposed. The measured permittivity of oil‐paper samples is fitted based on the Cole–Cole model with single dielectric relaxation process, and then simplify the fitting model. The structure coefficient per unit length (PUL) corresponding to the complex capacitance of the TWs can be obtained based on the finite element software FEMM. Combining the simplified model with the structure coefficient, the fractional admittance PUL of TWs is derived. Then the fractional transmission line model of the TWs is determined. Finally, the calculated results of fractional transmission line model considering the frequency‐dependent parameters are compared with the experimental measurements, and the results demonstrate the accuracy of the proposed model. [ABSTRACT FROM AUTHOR]

This study reports an investigation on space charge distribution and leakage current (LC) pulses of four units of glass insulators recently removed from service. Simulation works were conducted using finite element software and validated by laboratory experiments. The simulation and experimental results were found to be in good agreement when studying the space charge distribution pattern along the glass insulator string. It is evident that the LC waveform can be used to characterise the types of partial discharge according to their occurrence with respect to the AC supply. Thus, the proposed method is viable and reliable to be applied in an online measurement system. [ABSTRACT FROM AUTHOR]

This study presents the procedure of generating simple‐to‐apply engineering recommendation for earthing systems and boundaries for setting of earth faults relay protection in power systems with solidly earthed neutral. The simple rules are based on 'the worst case analyses'. Motivation for this work was simplification of the engineering process with acceptable deviation from economic optimum. Another reason is addressing the specific problems occurring in studied arid desert terrains conditions, which are described in this study. The analyses are based on calculation of earth fault current, its distribution over multiple earthing systems along the power line connected via protective conductor, tripping time dependent on relay curve, and allowed step and touch voltages depending on tripping time and characteristics of soil and optional additional surface material. For these calculations, the Excel/VBA software tool is developed and used. Different topologies of earthing systems (with grounding contours, rods, with/without backfill materials, etc.) considering layout of equipment in substation are studied using finite‐elements software in order to determine the ratio of touch and step voltages to ground potential rise – GPR. The methodology is explained through a prominent case study of overhead line with overhead ground wire and metallic poles in the rural area. [ABSTRACT FROM AUTHOR]