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Generation and transmission unit outages cause MW line overloading and bus voltage magnitude violation problems in the remaining part of the system. This paper presents a new method for bus voltage magnitude screening for transmission line and transformer outages. Classification and ranking errors of sensitivity-based methods are overcome by imposing a non-linear constrained optimization module on the well-known linear feed-forward computational algorithms. Genetic algorithms are preferred as computation tool because of its implementation simplicity as well as for its parallel processing advantage in future computers. Accuracy of the method is tested on IEEE 57-bus test system and IEEE 118-bus test system. The results are compared with those of the full load flow to verify the strength of the method proposed in this paper. [ABSTRACT FROM AUTHOR]

This study presents the influence of corona rings on impulse withstand performance of 380 kV V-insulator strings. Those strings comprising cap-and-pin type glass insulator units are one of the most common configurations in Turkish National Power Transmission System. Laboratory test setup was constructed for the centre phase of a full scaled tower. Laboratory tests are performed to investigate the lightning and switching impulse performance of the strings equipped with the existing racket type corona rings and the circular type corona rings. Withstand voltages, lower flashover probability levels, flashover routes and times to flashovers are determined under dry and wet test conditions. In addition, some 3D field simulations regarding potential and electric field distributions are also performed for the interpretation of insulator surface flashovers. [ABSTRACT FROM AUTHOR]

This paper presents corona ring optimization for 380 kV V-insulator string composed of glass insulator units. The influence of the corona ring design parameters are examined not only with regard to 3D simulations but also laboratory tests. The purpose of the simulations is to find reasonable corona ring design parameters such as corona ring diameter, corona tube diameter and installation height on the point of effective field regulation around the critical region of the string. Indoor laboratory tests including radio interference voltage levels, corona inception voltages and ac flashover voltages are conducted on the centre phase of a full scaled tower both for experimental based corona ring design as well as verifications of the simulations. After both simulations and experimental based investigations, appropriate corona ring design parameters for the string are determined for effective field regulation, minimum interference level, ac flashover performance and economic point of view. [ABSTRACT FROM AUTHOR]