ABSTRACT The main purpose of the substations grounding systems is to ensure integrity of substations equipment and safety of personnel in and outside of substation at the maximum fault currents. To meet safety requirements, grounding system should have a low as possible resistance. In order to achieve low resistance, grounding systems are designed in a way to achieve as large as possible contact surface between the grounding system conductors and the surrounding soil. On the other hand, cost – efficiency of the proposed solution must be taken into account. Therefore, to meet the technical criteria on the one hand and economic criteria on the other hand, grounding systems are composed from large number of horizontal, vertical and inclined galvanic connected unisolated conductors that in most practical cases form complex geometries. Additionally, soil in which grounding systems are placed is almost always composed of a number of layers with different electric conductivity. In this paper, numerical model based on the indirect boundary element method is presented for calculation of grounding system parameters placed into the vertically layered soil.

This paper presents the detection method and analysis methodology of dynamic stray current effects on underground pipelines based on simultaneous multiparametric measurements in combination with continuous wavelet cross‐correlation and frequency plots. Measurements presented within this paper were conducted at two locations experiencing tram induced dynamic stray currents, in the first case, on unprotected pipeline and in the second case, on pipeline under cathodic protection. On both pipelines, measurements of pipe‐to‐soil potential, lateral potential gradient, corrosion probe current, and pipeline current were simultaneously done for time period of 20 min. For both locations, the two wavelet cross‐correlation spectrograms for the quantities: lateral potential gradient and probe current versus pipe‐to‐soil potential show that 5% statistical significance levels are in periods between 16 and 128 s. Time spans and period lengths of observed cross‐correlations on spectrograms reflect the stray current influence that may be linked to specific events, such as passing of trams. On the other hand, frequency plots of the measured quantities give clear visual representation of the time that pipeline spends in a certain state related to the possible harmful effect of stray current and also show the degree of cathodic protection beneficial effect.

In this article the summary of measurement and calculation values of low frequency electric field radiation around the high-voltage transmission lines and impact of the increased voltage values on the AC corona onset voltage gradient are presented. The measurements of the low frequency electric field radiation level were performed under the 400 kV transmission lines of horizontal configuration with standard and compact dimensions. In all cases analyzed in this article, the measurements are performed in the middle of the span, because at this point the conductors are closest to the ground. The analysis in this article has been initiated by the increased voltage values of long duration that have been registered in nodes of the 400 kV network in Bosnia and Herzegovina and the neighbouring countries during the last years. The calculation of the low frequency electric field radiation of the different configuration of the high-voltage transmission lines will be useful for determining the non-ionization radiation exposure levels of the general public in the future as well as to determine their impact on the AC corona onset voltage gradient.

The pa per dis cusses the pos si bil ity of im prov ing the char ac ter of gas surge ar rest ers. Ex am ined were: the mag netic field ef fect, the ef fect of the hol low cath ode, and the ef fect of the al pha ra di a tion source 241Am. Nu mer i cal and real ex per i ments con ducted are pre sented to gether with the o ret i cal in ter pre ta tions of the ob tained re sults. Real ex per i ments were car ried out on a model of a gas surge ar rester spa tially con structed for ex per i ments pre sented in this pa per. The model was de signed in such a way that it was pos si ble to change all the rel e vant pa ram e ters of the gas surge ar rester model. Ex per i ments were con ducted un der well-con trolled lab o ra tory con di tions. The tests were per formed with d. c. and im pulse volt age. The re sults ob tained by ex per i ments were pro cessed by so phis ti cated sta tis ti cal meth ods. The ex pressed mea sure ment un cer tainty of the ex per i men tal pro ce dure showed a high sta tis ti cal re li abil ity of the ob tained re sults. Based on the re sults of the re search, the model of a gas surge ar rester, in which the ef fect of the hol low cath ode and the ra dio ac tive source 241Am were com bined, un am big u ously proved to have the best char ac ter is tics.

The electric power network in Bosnia and Herzegovina on the 400 kV voltage level built up in the 70’s of the last century, has an important role for the electric energy exchange. Its parts are more than 40 years old. The paper investigates the impact of daily variations of the atmospheric conditions on the AC corona onset electric field. The AC corona onset electric field on overhead transmission lines is affected by a several factors. Besides the conductor dimensions, the atmospheric conditions have the largest impact on the value of the relative air density as well as the surface conductor roughness. The relative air density is a function of the ambient temperature and pressure. Ambient temperature at any given location is subject to daily and seasonal variations. The ambient pressure is not subject to large daily variations. The sag of the overhead transmission lines increases by an increase of the conductor temperature due to the electric load and specific atmospheric conditions. Increased voltages increase the value of the electric field and can presents risks for the exposure of human beings. Also, high voltages in the network cause high power losses due to the AC corona.

State estimation is a basic function, which results are used in almost all other functions for the analysis, management and planning of distribution networks. The paper describes the process of load calibration that is one of the basic steps in the process of state estimation in the distribution network. Algorithm for state estimation of a radial distribution network used in this paper is based on a modification of the algorithm for load flow calculation. For the calculation of load flow of radial distribution networks “backward-forward” algorithm was used. The developed application for the state estimation is used for state estimation of a real radial distribution network.

Cathodic protection (CP) is a technique that prevents corrosion of underground metallic structures. Design of any CP system first requires defining the protection of current density and potential distribution, which should meet the given criterion. It also needs to provide, as uniform as possible, current density distribution on the protected object surface. Determination of current density and potential distribution of CP system is based on solving the Laplace partial differential equation. Mathematical model, along with the Laplace equation, is represented by two additional equations that define boundary conditions. These two equations are non-linear and they represent the polarization curves that define the relationship between current density and potential on electrode surfaces. Nowadays, the only reliable way to determine current density and potential distribution is by applying numerical techniques. This paper presents efficient numerical techniques for the calculation of current density and potential distribution of CP system based on the coupled boundary element method (BEM) and finite element method (FEM).

This paper deals with investigation of the impulse characteristics of transmission line tower grounding. Investigations of the impulse characteristics of transmission lines tower grounding in this paper are based on experimental analysis conducted on type “A” grounding of transmission line tower. Firstly, paper describes the problem of back-flashover and impact of transmission lines tower grounding impedance on it. Also, experimental investigation of impulse characteristics with different rise time of current wave front on real type “A” grounding are given. Finally, detail analysis of experimental data is given.

This paper considers the effect of the discontinuity of electrolyte electrical conductivity on the distribution of potential and protective current density in cathodic protection systems with galvanic anodes. Its aim is to present a simultaneous application of both analytical and numerical models for the calculation of the distribution of protective potential and current density in the cases of homogeneous and double-layer electrolyte. For non-linear boundary conditions at the electrode surface (secondary distribution of protective current density), the indirect boundary element method is used, because of the complexity of calculation for which collocation at the point method was used. The calculation is further complicated due to the nonlinearity of boundary conditions at the electrode surfaces. In order to show the importance of this analysis, calculations for the observed system as well as of errors caused by neglecting the boundary discontinuity of the soil conductivity are provided. Based on these calculations and error analyses, the impact of the double-layer electrolyte on the correct calculation of the cathodic protection system with galvanic anodes is evaluated. This paper also provides the analysis when the double-layered nature of the electrolyte can be practically ignored, which is of great importance to designers of these systems.