Protection against lightning overvoltages in power distribution systems

ABSTRACTMaster Degree ThesisPROTECTION AGAINST LIGHTNING OVERVOLTAGES INPOWER DISTRIBUTION SYSTEMSAhmet Turan ÖZCANInonu UniversityGraduate School of Natural and Applied SciencesDepartment of Electrical and Electronics Engineering81+viii pages2005Supervisor: Assoc.Prof. Dr. M. S. MAM ŞThe purpose of this thesis is to analyze the transients caused by indirect lightningstrokes in power distribution systems and to examine protection methods against lightningovervoltages.In power distribution networks and transmission systems, overvoltages much greaterthan the system normal voltages may arise due to lightning strokes. These overvoltages maycause harmful effects on the system compenents; such as isolator break-down, short circuitfaults and malfunction of the system equipment. Determination of transient overvoltagescaused by direct or indirect lightning strokes is important for protection of the powertransmission and distribution lines and minimisation of harmful effects. The results obtainedfrom numerical solution of mathematical models of transmission lines using computerprograms provide information about the level of overvoltages and hence it leads to prevent thetransient voltages.In this study, the induced voltages due to lightning stroke near a distribution line areobtained using EMTP and by written computer programs in MATLAB environment. Theeffect of distance to stroke point and distance between the paralel conductors, one of which issubjected to a lightning stroke is investigated. The concluded remarks for protection ofdistribution systems against lightning strokes are given.KEYWORDS: Power distribution system, lightning surge, transmission line, EMTP,MATLAB.