Irfan Turkovic

Application of finite element method in calculation of large and complex grounding systems

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.

Numerical model for calculation of parameters of cathodic protection system with galvanic anodes

This paper presents the use of coupled BEM/FEM method by the numeric calculations of protection current/potential distribution when the cathodic protection system with galvanic anodes is applied. Cathodic protection (CP) system is very efficient system for protection of underground metal object from corrosion. The most important phase by installing the CP system is to optimally and correctly defines the distribution of the protection current. There are many correlation related factors that influence the dimensioning of CP elements and the time of their design. The distribution of protection current/potential in systems of cathodic protection is governed by the Laplace equation, with the usage of corresponding predefined boundary conditions. Field data are obtained during the installation of the system and periodical field measurements during the exploitation of cathodic protection system with galvanic anodes. In this paper, acquired field data are compared to the values that were obtained using numerical calculations. Deviations between these data are negligible. Values of protection current/potential are most influenced by values of soil resistivity between anode and cathode surface.

Modelling of the cathodic protection system with dynamic non-linear polarization characteristics

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.

Numerical calculation of floating potentials for large earthing system

During the malfunction in the substation, there is danger that transferred potential from the earthing system area into the outer space may occur. This problem may be a limiting factor when calculating the earthing system. Generally, a danger from too high touch voltage occurs. Also, very large potential differences are possible. Calculation of the transferred potential in substation should be given special attention. Superposition procedures are often used in literature for calculation of transferred potentials with which it is needed to solve two or more large full systems of matrixes. Direct approach to forming and solving of modified matrix of potential coefficients by applying Galerkins procedures of weight residue in indirect method of boundary elements is considered in this paper. At the end of the article considered model was presented on example of calculation of a large steam power plants main ground electrode.

Automatic Compensation Coil-Petersen Coil in Distribution Grid

The introductory part of the paper gives the basic theoretical considerations of the ways of neutral point treatment in distribution grids with special reference to the method of neutral grounding of distribution transformers by a compensation coil. The second part gives the analysis of the use of compensation coil as a future choice of neutral point grounding on the particular distribution grid TS 35/10 kV Bjelasnica. Also, the paper has conducted analysis of the available data and techno-economic analysis of neutral points grounding of transformers in TS 35/10 kV Bjelasnica in case of transformer neutral grounding by low ohmic resistor and in case of resonant neutral point grounding. In addition to the analysis of the (available) measured values, the adequate dynamic models of distribution grids are made by using the EMTP software package and calculations for neutral grounding by the compensation coil are done, as well as in the case of isolated grids, and a comparison of the results of ground fault currents was made.

Functional relationship between cathodic protection current/potential and duration of system deployment in desert conditions

In this paper we analyze functional correlation of the attenuation of protection current/potential in cathodic protection (CP) systems over the time. Our aim is to define protection current/potential function in correlation to CP system exploitation time, based on long term measurements of the current/potential. Correlation of the attenuation of the protective current/potential over the time period is established by comparison of the experimental data and data obtained from our analytical model. The analytical model allows prediction of the changes in the changes in the current/potential over the time and thus prediction and verification of the CP. Our data are collected for cathodic protection PCCP (Prestressed Concrete Cylinder Pipe) in desert conditions. Usage of our model for the attenuation of protective current/potential over time of exploitation of a CP system significantly simplifies operational procedures and saves on time, equipment and measurements. Application of proposed mathematical model, make it is possible, without long-lasting measurements, reliably envisage evolution in time of a cathodic protection system.

Application of the coupled BEM/FEM method for calculation of cathodic protection system parameters

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).

Forecasting PM10 concentrations using neural networks and system for improving air quality

In this paper using Artificial Neural Network (ANN) are presented forecasting results of PM10 concentrations for the city of Sarajevo. Input data of the proposed model are meteorological variables (wind speed, humidity, temperature and pressure) and pollution variable (PM10 concentration) recorded in the Federal Institute for Hydrometeorology from 2010 to 2013. The proposed model is tested on the several cases and the results are satisfactory. The results of the forecasting show the different effects that certain meteorological parameters have on the temporal prediction of concentrations of PM10. It can also be concluded that ANN approach is very useful in terms of the time series forecast the concentrations of PM10 particles with good forecasting results. Also, it is presented the idea of a unified system for air quality improvement, which involves a variety of systemic measures in the areas affected by an increase of PM10 concentrations.

Evaluation of the quality of impulse high voltage measuring system

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.

Impulse noise influence on communication system in high-voltage substation

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. Disconnectors 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.