Dragan Tasić

Analysis of a MV XLPE cable termination design with embedded electrodes

Insertion of embedded electrodes (EEs) inside a MV XLPE cable termi- nation strongly affects electric field around the terminati on and accordingly must be carefully considered. In this paper, influence of embedded e lectrodes on voltage distri- bution in some constructions of the 20 kV cable terminations was analyzed. Different options were considered for a specific number of the EEs along the cable insulation surface, taking into account possible effects of floating or grounded EEs, their differ- ent position and separation. In every option, a basic method of stress relieving with resistive layer over the end of semi conducting screen and primary cable insulation was applied. Reference design was a cable termination without EE. Its voltage dis- tribution, total electric field and tangential component we re observed for comparison. The stress relief materials, in the shape of pads or tubes, we re used. Their properties were kept the same in all constructions. Voltage distributi on was monitored, starting from the end of the primary cable insulation in the vicinity of the phase conductor and ending at the cable insulation attached to the semiconducting screen end at ground potential. The different design options were experimentally verified.

New EEM/BEM hybrid method for electric field calculation in cable terminations

From the aspect of design and operation, cables and cable accessories are still very actual. Technological developments and the increasing need for electricity cause wider everyday cable termination applications. To ensure reliable performance over the cable system lifetime, design concepts, based on numerical calculations, must be correct. An Equivalent Electrodes Method/Boundary Elements Method-hybrid approach that allows electromagnetic field calculations in multilayer dielectric media including inhomogeneous regions is presented. Applications of the method to electric field calculations in cable terminations with finite thickness of dielectric stripes and stress cones are presented. Electric field distribution is considered for multilayer dielectrics with constant dielectric permittivity. The proposed method obtained results are compared with values obtained by using the finite elements method. It is shown that application of this hybrid numerical method is easier than the finite elements calculations in complex regions, and that the high degree of accuracy is achieved along with saving the computational time. A number of different constructions of cable terminations are experimentally verified using the proposed hybrid method.

The grounding system of the pillar on the road

The lightning pillars on the highway need to be grounded in accordance with the corresponding standards. A procedure for characterization of the grounding systems placed inside the road is presented in the paper. The road is treated as a ground inhomogeneity. Using the estimation method, the road is approximated by a domain having semi-circular cross-section. The analysis includes application of the quasi-stationary image theory and the Greens function for the point source placed inside the cylinder of the semi-circular cross-section. Leakage current distributions are obtained applying the Method of Moments. Afterwards, the grounding system characteristics are determined.

The analysis of typical seasonal load duration curves of low-voltage consumers

The paper presents some typical daily load curves formed by averaging data collected by the system for remote energy meter reading in time period longer than two years. Data from nearly 7000 energy meters at low–voltage consumers are processed, statistically reliable daily load curves are obtained and their characteristics are listed. Typical load duration curves of months belonging to winter and summer season are formed on the basis of daily load curves and depicted in the paper. These seasonal load duration curves of different load classes at low voltage are mutually compared. The influence of different number of working days, Saturdays and Sundays on monthly load duration curves is discussed, and corresponding load factors and loss factors for winter and summer months are statistically analysed.