Transmission Line Essay

958 Words4 Pages
INTRODUCTION TRANSMISSION LINE Generators and loads are connected together through transmission lines transporting electric power from one place to another. Transmission line must, therefore, take power from generators, transmit it to location where it will be used, and then distribute it to individual consumers. A ROT: the power capability of a transmission line is proportional to the square of the voltage on the line. Therefore, very high voltage levels are used to transmit power over long distances. Once the power reaches the area where it will be used, it is stepped down to lower voltages in distribution substations, and then delivered to customers through distribution lines. Figure 1 Dual 345 kV transmission line Figure 2 Distribution line with no ground wire The transmission lines are mainly classified as short, medium or long line it is based on the accuracy of the model and simplicity. Short line model is quite simple, the long line model is somewhat complex and the medium line is in-between the two. At power frequency of 60 or 50 Hz, the lines of length below 80 km are treated as short lines and the length of line exceeding 80 km but less than 250 km can be modelled as medium lines and as the length of lines exceed 250 km it is long line. For short and medium length lines the parameters are lumped. This simplifies the model and gives quite accurate result. In case of the long transmission lines the line parameters are considered as distributed along the length of the line. The aim of the transmission line model is that it should be simple and the analysis of the model should bear desired accuracy. Short Lines Transmission line below 80 km length can be modeled as short lines. The transmission line is a three phase system and here assumed as balanced due to transposition and balanced load at receiving end. In Fig3 is shown a short

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