Salih Carsimamovic

Very fast electromagnetic transients in air insulated substations and gas insulated substations due to disconnector switching

Very fast electromagnetic transients (VFT) in air insulated substations (AIS) and gas insulated substations (GIS) caused by switching operation of disconnectors are investigated. Results obtained from very extensive field tests and from digital simulations as well as a comparison between field tests and calculation results of VFT in AIS and GIS due to disconnector switching are presented. Field tests of disconnector switching in 220 kV air insulated substations Grabovica and Kakanj as well as test circuit of 110 kV GIS section are performed. Digital simulation of VFT for different models of power network are performed using EMTP-ATP.

Experimental results of ELF electric and magnetic fields of electric power systems in Bosnia and Herzegovina

Investigations of electric and magnetic fields on 400 kV transmission lines Tuzla-Visegrad, Sarajevo 10-Sarajevo 20, Tuzla-Ugljevik and 220 kV transmission line Kakanj-Zenica are performed. These transmission lines are important objects for operation of electric power system of Bosnia and Herzegovina. In the paper measurements of extra low frequency (ELF) electric and magnetic fields (EMF) of single 220 and 400 kV overhead transmission lines with flat conductor arrangement but with different horizontal distances between phases and different heights above ground are presented. These electric and magnetic field measurements are also compared with calculations results performed with two software programs (one commercially available and one developed by authors on the base of a solver). Also, in the paper the parameters influencing electric and magnetic fields measurements are investigated.

Influence of Resistance of Electric Arc on Transients Due to Disconnector Switching in Air-Insulated Substations

In this paper, switching overvoltages due to disconnector switching in air-insulated substations (AISs) are presented. Measurements of these switching overvoltages were performed in the AIS Grabovica (Hydro Power Plant-HPP Grabovica) on River Neretva and the AIS Kakanj (Thermo Power Plant-TPP Kakanj). These power plants are important objects for operation of Bosnia and Herzegovinas electric power system. Investigations of operating of air-disconnector-type centre break was performed in order to determine switching-overvoltage levels on primary and secondary circuits that can lead to relay tripping in AIS Grabovica and AIS Kakanj. During operations of disconnector (synchronization or disconnecting of generator from network), malfunctions of signaling devices and burning of supply units of protection relays appeared. At the same time, sparking between primary terminals of the instrument current transformer occurred. The influence of resistance of electric arc between the contacts of the disconnector is analyzed. Computer simulations by means of alternative transients program-electromagnetic transients program are performed. Differences between the measured and the calculated values were under 4.52% for overvoltage factor and under 2.56% for overvoltage wave frequency. Comparison of the transient computer simulations with the field measurements showed that calculations could be used for the assessment of the transient overvoltages caused by disconnector switching.

Computer Simulation of Transients Due to Disconnector Switching in Air-Insulated Substations

Switching overvoltages due to disconnector switching in air-insulated substations (AIS) are presented. Analysis of shape and levels of switching overvoltages by means of experimental and computing investigations on 220 kV switchyards of Thermo Power Plant (TPP) Kakanj are presented. Computer simulations by means of EMTP-ATP [1] are performed.

Electric Field Calculation on Surface of High-Voltage Transmission Line Conductors

This paper presents a calculation of the value of the electric field on the surface of the conductors and in the immediate vicinity of the high voltage transmission line of 400 kV level. For the calculation of the values of the electric field, the CSM method is used. Verifying the established model was carried out by comparing the calculation results with results of measurements of the electric field at a height of 1 m above ground level. Measurements of the value of electric field lines below the height of 1 m above ground were carried out over the years in Bosnia and Herzegovina. The measurements and calculations were carried out on 400 kV lines of standard dimensions and reduced dimensions. Using the established model, values of the electric field on the surface of the conductors and in their immediate vicinity were calculated. The calculated values of the electric fields are used to determine the corona onset voltage gradients.

Calculation of the corona onset voltage gradient under variable atmospheric correction factors

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.

Modeling and Calculation of Switching Overvoltages in 400 kV Electrical Networks

Results of investigation of switching and temporary overvoltages onto 400 kV electrical networks before and after reconnection of electric network of the South-East Europe with other part of European electric network in UCTE zone are presented. Investigations are performed at 400 kV overhead lines Banja Luka-Tuzla and Mostar-Konjsko (Croatia), using EMTP-ATP. Validation of simulating model are performed at 220 kV electrical network, transmission line thermo power plant Kakanj-Switchyard Kakanj, where switching overvoltages were measured