Double-Circuit Transmission Line
The double-circuit transmission line is a transmission line, which has two circuits carried through the electric tower line. The double-circuit transmission line consists of two circuits. In the three-phase electrical system and every tower insulates and holds six conductors. Single phase alternating current power lines which is used for the traction current and have four conductors for two circuits. Generally both the power circuits functions at the same voltage.
Construction of the double-circuit transmission line is as follows:
The lattice tower structure generally has the pyramid base and a vertical section and three levels of crossarms which are extend at each side of the phase. The insulators are fixed to the crossarms. Generally, the common type of double-circuit transmission line has the two center crossarms, which is quite longer than the other two pairs however sometimes there are also in the same size. An alternative which is at times used in Europe , which has two lengthy crossarms that carry two conductors on each and then two standard crossarms above that. The steel pole construction has a very thick single pole which has a total of six crossarms fixed to it. In the HVDC systems generally two conductors are carried on each line however sometimes only one of the pole system us carried on a set of power towers. In some of the countries such as Germany, many of the power lines which has voltages more than 100 kV are using the double-circuit transmission line or quadruple or in some cases even the hexuple power line since rights of method are rare. At times all the conductors are fixed with the erection of the electrical pylons or towers; generally some of circuit lines are fixed later.
One of the main disadvantages of the double circuit transmission lines system is that the maintenance works could be more complicated. While working with such type of lines the two circuits should be switched off complete, since it has high voltage and proximity to such lines could be very danger. Also in case of failure or breakdown both the systems are greatly affected.