State-space modeling and analysis of distributed parameter line model

Accurate analysis of transients is of paramount importance for the reliability, continuity and stability of power systems. Especially time-dependent fast-changing events such as atmospheric pulses, sudden load changes, short circuits and switching operations create high voltages and currents in the system elements, both straining the insulation system and adversely affecting the power quality. In this thesis, various transient analyses of a single-phase transmission line have been performed. Conditions such as line switching with a power transformer connected to the transmission line, lightning strikes on the loaded transmission line, lightning strikes on the transmission line with a power transformer connected to the end of the line, fault occurrence after switching on the transmission line and fault occurrence after lightning strikes are discussed. In transient studies, transmission line with distributed parameters, Heidler lightning model and power transformer with disk type winding structure are used. The transient analysis of all models is performed by the state-space method. Inductor currents and capacitor voltages are selected as state variables and trapezoidal integration method is used to solve the equations of state. The equivalent circuit used in the state-space method is drawn and simulated in ATP-EMTP. The results of both methods were compared and it was found that the results obtained supported each other. In the study, the effects of varying the values of fault resistance, grounding resistance and step interval on voltage distribution, waveforms and maximum voltage levels were analyzed in detail. The proposed method effectively models the voltage-current characteristics of the transmission line and transformer windings during transients. It is concluded that the state-space approach is a viable option for transient analysis in power systems and can contribute to the design of protection devices and winding insulation.