. This paper deals with a combined computer-aided numerical – analytical approach to calculation of the grounding. The electromagnetic theory on which the presented mathematical model is based is described. The model which is based on boundary element method, Aitken's δ 2 algorithm and grounding potential non-uniformity correction factors is explained in detail. A special attention is paid to the selection of an appropriate Green's function in the calculation of parameters of a large and complex grounding mesh for a homogeneous and a two-layer soil. Finally, the model is used to calculate the grounding mesh parameters of a real power substation with complex geometry.

Cathodic protection systems are used for protection of underground or underwater metallic infrastructure against corrosion. Protection by cahtodic protection system is achieved by polarizing protected object i.e. by shifting equilibrium potential to more negative value. Value of the electric potential and current density on the surface of protected object are essential data for evaluation of efficiency of the cathodic protection system. Value of these parameters can be determined by using numerical techniques. This paper deals with the mathematical modeling of cathodic protection system when taking into account dynamic nonlinear polarization characteristics on the electrode surface. Firstly, mathematical model is described in detail. Numerical procedure presented in this paper is divided in the two parts. First part is the calculation of distribution of electric potential and current density in spatial domain using direct boundary element method, and calculation of the time changes of these parameters by finite difference time domain method. Finally, presented mathematical model was used for calculation of parameters of one geometrically simple cathodic protection system example.

Corona phenomena on conductors are of importance for high voltage transmission lines. In this paper a calculation of the corona onset voltage gradient of AC conductors has been performed for taking into account the effects of atmospheric conditions. Corona characteristic on overhead transmission lines (OHTL) are influenced by a several factors. The conductor surface roughness and atmospheric conditions have a direct influence on the corona onset voltage gradient. Atmospheric conditions have the largest influence on the value of the air density. The air density is function of the ambient temperature and pressure. Ambient temperature at any given location is subject to daily and seasonal variable. The transmission line crossing a high humidity area and thus humidity should be taken into account in evaluating of the corona onset voltage gradient. Increased voltages in the 400 kV electric power network of Bosnia and Herzegovina are increasing the value of the voltage gradient and higher power losses due to AC corona. Therefore, it is important to determine the value of the voltage gradient on conductor surface as well as corona onset voltage gradient to accurate determined power losses due to AC corona.

This paper deals with method for evaluation of quality of the impulse high voltage measuring system. The purpose of assessing the quality of the impulse high voltage measurement system is to determine whether the measurement system is suitable for use in the appropriate measurements. Firstly, paper describes components of impulse high voltage measuring system. Main characteristics of measuring systems used for evaluation of quality of impulse high voltage measuring system are explained in detail for the characteristics of the measuring system. Finally, test method based on the comparative experimental and numerical analysis is given.

Cathodic protection (CP) is a technique that is used for protection of underground and underwater metallic structures from corrosion. Design of cathodic protection system requires defining of protection current density and potential. These parameters must meet given criterions during the exploitation of cathodic protection system. This paper deals with problem of modelling of the cathodic protection systems with dynamic non-linear polarization characteristics. Firstly, paper describes dynamic non-linear polarization characteristics. Mathematical model based on combined Boundary Element Method and Finite Difference Time Domain Method with assumptions on which is based are explained in the following part. Finally, application of the presented mathematical model was done on one geometrically simple example.

Paper presents a calculation of the electric field distribution around the 400 kV transmission lines in power system of Bosnia and Herzegovina (B&H). Method of equivalent charges was used for the calculation of the electric field at arbitrary points in the vicinity of high-voltage transmission lines. Transmission lines with standard tower's dimensions, as well as lines with reduced (compact) tower's dimensions were considered. Comparisons between calculated and measured results of electric field values around the transmission line with the standard dimensions of the tower on 400 kV line Sarajevo 10 - Sarajevo 20 was performed.

In the paper the results of measurements of voltages and electric fields of extra low frequency (ELF) below 400 kV transmission lines in Bosnia and Herzegovina (B&H) are presented. In the high-voltage network in B&H there were registered a significant number of power frequency overvoltages in the regime of small loads after its reconnection in common energy system UCTE (Union for the Coordination of Transmission System Operators for Electricity), and today ENTSO-E (European Network of Transmission System Operators for Electricity) in October 2004. Increased voltages in the high-voltage network causes increase in the value of electric field and exposure of human bean to electric fields. On the other hand, high voltages in the network causes higher power losses due to AC corona. Therefore, it is important to determine the value of electric field in the vicinity of high-voltage lines to assess their effects on people and equipment as well as value of electric field at increased voltages to accurate determined power losses due to AC corona. The results of measurements of electric fields in the spatial profiles at 1, 2 and 3 meters above ground at distances up to 20 meters from line are presented.

This paper deals with design of the substation grounding system by using computer. As it is well known, proper design of the grounding system is most important part of the whole project of the substation, from safety point of view. Procedure of the measurement of the soil resistivity and interpretation of the measured results is given. Interpretation of the soil resistivity data and results of interpretation are explained. Also, calculation procedure of potential distribution of the complex grounding system, grounding system resistance, distribution of touch and step voltage by using a computer are presented. Whole procedure was implemented on the real substation grounding system. Results of the potential distribution on the ground surface of substation touch voltages and step voltages are calculated in the paper. Finally, analysis of the capacitor bank's underground steel construction influence on all relevant parameters of the grounding system is given in this paper.

This paper analyzes the phenomenon of potentials deviation (ON/OFF potentials) as a result of changes in the soil resistivity, when applying cathodic protection systems with galvanic anodes on PCCP (pre-stressed concrete cylinder pipes) in ambient desert conditions. Measurement of ON and OFF potentials on a long section with different values of the soil resistivity have shown that there are great deviations in parts of sections which are proportional to the measured values of the soil resistivity. Analyzing the changes in a value of IR drop show that the ON potential changes very little in the case of high values of the soil resistivity, as well as that on these sections, a high value of IR drop appear, i.e. great change OFF potential. Over time, this difference between the ON and OFF potentials in these sections decreases and this is a case of a full polarization of PCCPs. If the value of the electrical soil resistivity is relatively low, it can be concluded that the IR drop is negligible.

This paper focuses on the optimization of the design of high voltage transmission lines in order to reduce the negative impact of electric and magnetic fields. Within this paper the results of measurements of electric and magnetic fields near 400 kV transmission line were presented. Measurements were performed in the middle of the range between two towers, because at this point transmission lines are closest to the ground. In order to make better validation of the used calculation models of electric and magnetic fields, measurement of temperature, pressure, humidity and height of particular transmission lines in the middle range, were performed simultaneously. The values of current and voltage on the transmission line, at the time of measurement of the fields, are also given. Based on the measured values of electric and magnetic fields, validation of calculation was performed. This paper also contains a brief comparative analysis of regulations on non-ionizing radiation of power facilities that are in use in some European countries, as well as recommendations of the International Commission on Non-Ionizing Radiation Protection (ICNIRP). Calculation of electric and magnetic fields of different configurations of 400 kV transmission line, were performed in order to find optimal solution in terms of reducing the negative impact of electric and magnetic fields of high voltage transmission

This paper presents measuring results of transferred overvoltages in the secondary circuits of instrument transformers caused by switching operations of disconnector in air insulated substations 220 kV, in Bosnia and Herzegovina. Obtained results show that the maximum amplitude of these overvoltages can be up to 940 Vpeak (220 kV hydroelectric power plant Grabovica). In order to ensure electromagnetic compatibility it is necessary to adequately damp high overvoltages by instrument transformer, or to use some of the measures for reducing transferred overvoltages in secondary circuits. The conducted measurements show that in case of using unshielded secondary cables on current transformer terminals, overvoltages are much higher than in case of using shielded cables (3.7 times higher in measuring core and 6.1 times higher in protective core). Paper gives suggestions for eliminating the causes of interference, reducing coupling on the path of signal transmission and increasing protection from interference in the secondary devices.

Grounding systems have the most important role in safety of staff and substation equipment and therefore they require detailed analysis of relevant parameters. This paper discusses the possibility of application of software packages based on finite element method (FEM), when conducting analysis of grounding systems. Firstly the paper describes a mathematical model with assumptions on which is based. Complex grounding grids buried in both single-layer and double-layer soil where analyzed. In order to verify the presented model, calculation results are compared with results of various analytical and numerical methods, as well as with measured results. Finally to show the practical application of this approach, an example of a real grounding grid is calculated.

Investigations of the electromagnetic interference indicate that disconnecting switching of the off-loaded busbars is one of the most important sources of electromagnetic interference in the secondary circuits of a power station. Disconnector's contacts in air-insulated substations (AIS) move slowly causing numerous strikes and restrikes between contacts. Every strike causes high-frequency currents (from a few hundred kHz to a few MHz) tending to equalize potentials at the contacts. These travelling current and voltage waves are the most important sources of electromagnetic coupling to the secondary circuits of instrument transformers, on whose ends high-speed and low-power electronic devices are connected. During disconnector switching malfunctioning of auxiliary circuits can occurred. In this paper results of measurements of overvoltages in the secondary circuits in the AIS Grabovica (Hydro Power Plant - HPP Grabovica) and AIS Kakanj are presented. In order to reduce overvoltages in secondary circuits, measures for mitigation of electromagnetic interference are presented.

In real high voltage systems, it is necessary to observe system parameters. Depend on investigated values, it is possible to detect malfunctions or overvoltage in high-voltage substation. Because of these, communication system in actual high voltage substation is implemented. In the high-voltage substation disconnector and circuit breaker are installed, whose operation causing appearance of impulse noise effect in the present communication system. Disconnector's contacts in air-insulated substations (AIS) are moving slowly causing numerous strikes and re-strikes between contacts. Every strike causes high-frequency currents (from a few hundred kHz to a few MHz) tending to equalize potentials at the contacts. These processes are the source of impulse noise in the connected communication system. In this paper measured impulse noise level and estimate influence to probability of false alarm appearance in the communication system are presented.