Ph.D. THESIS

 

Matislav Majstrović, Stohastic Approach to Fault Current Calculation, Ph. D. Thesis, University of Zagreb, Faculty of Electrical Engineering and Computing, Power System Department, Zagreb, Croatia, April 8, 1986

 

Description: The thesis consists of six chapters. In the first chapter introductory explanations are given and the need for stohastic treatment of the fault currents is enhanced. The thesis deals with the three phase fault current but an analogous approach can be used for the other fault current types, too. Chapter two contains deterministic three phase fault currents calculation in the given bus for specified system state. For that purpose power plant electromotive forces have to be calculated first. In addition, a complex nodal voltage calculation during the fault condition is shown. At the end of this chapter, two ways of fault current calculation are given. In the first case fault currents are obtained using electromotive forces, while in the second case nodal voltages before fault occurance are used. Stohastic three phase fault current calculation for the specified system state using the method of estimation is analysed in chapter three. After presenting a stohastic approach of the electromotive forces calculation, the manner of stohastic nodal voltages determination during the fault condition is shown. At the end of the chapter an example of the stohastic fault current calculation on the appropriate test model is presented.

 

In order to validate the results obtained in the previous chapter, the method of stohastical modelling also known as Monte Carlo method is used. This method is shown in chapter four. In chapter five stohastic three phase fault current calculation for different system state using method of stohastic modelling is taken into consideration. At the beginning of this chapter description of pseudorandom number generators are given. In addition, outages of the system elements are considered as random events. Due to the existance of the hydro power plants with uncertanities in generations for each pseudorandom system state, possible constant and variable energy production of the hydro plants are analysed. After that, a reqired thermal plants power and energy productions are obtained. Using these results the unit commitment in the pseudorandom fault event is determined. At the end of this chapter mathematical model for nodal voltages and branch currents calculation. Due to the fact that stohastic calculation method is used, a choice of the the sample size is analysed as well. Theoretical considerations of this chapter are supplied with the results of the appropriate test model.

 

Conclusion made upon consideration in the previous chapter are given in chapter six. References and important notions are listed after chapter six. At the end of this thesis Appendix, containing both fault current module, angle covariance analyses and description of the software packages STOKS3, SKSMK and VSKMK are given.

 

Key words: fault calculation, stohastical modelling method, power system energy bilanca, unit commitment, model for fault current calculation

 

download will be available soon