Research On The Protection And The Fault Location Of The Transmission Lines On The Same Tower

The transmission lines on same tower have been widely used to reduce the costs of theconstruction of transmission lines and increase the transmission capacity of the width of thetransmission corridors. Because of the large number of circuits, the small distance andmurual inductance between the lines, the fault types of the transmission lines on sametower are more complex than the normal circuit or double circuit lines operated in parallel.It will bring much negative influence to the relay protection of the transmission lines on thesame tower. In recent years, Scholars at home and abroad have made many researches onthe relay protections of the transmission lines on the same tower and obtained manybeneficial results. However, the research of principles of relay protection has been done forthe double circuit lines on the same tower, but very little for the other transmission lines onthe same tower.So, it need more studies for the protection of incomplete-journey doublecircuit lines on the same tower.On the other hand, the existing schemes of dynamicsimulation experiment about high-tension overhead line are only applied to single-circuittransmission line and parallel double-circuit transmission line. The schemes of dynamicsimulation experiment about the double circuit lines on the same tower are needed to befurther studied. Furthermore, the research of the fault location about the double circuit lineson the same tower is based mostly on the assumption that the line parameters aresymmetrical at present. Otherwise, the accuracy will be badly affected when the actual lineparameters are asymmetric.So, the researches and analyses above relevant problems are ofgreat theoretical and realistic significance to helping the growth of the relay protection andfault location technology, to improving the grid safety level.The paper establishes the simulation platform by using PSCAD, which apply to thestructure and operation characteristics of incomplete-journey double circuit lines on thesame tower. On this basis, there are many simulation analysis are carried out, whichcontrapose the main challenges the protection relays may face, especially, when thedistance protection and fault-phase selectors are used to the protection ofincomplete-journey double circuit lines on the same tower. The analysis provided theoretical bases for improving and perfecting the performance of the relay protections.The problems in differential protection, distance protection, phase selector and thedirectional element, bought by the double circuit lines on the same tower, are analyzed andsummarized in the paper. It also analyses the special requirements of automatic reclosing inthe double circuit lines on the same tower. Combining with the existing high-voltagetransmission line protection dynamic simulation test specifications, put forward thedynamic simulation test scheme that is suitable for protection test of the double circuit lineson the same tower. It is useful to completely and objectively assess the overall performanceof the protection.The paper analyzes the performance of the present usual fault location algorithms for thedouble circuit lines on the same tower, points that it may increase the error when thepresent usual fault location algorithms are used in not completely transposed lines or notransposed lines. So the paper proposes the new fault location algorithm which is based oncalculateding the linevoltage distribution in every subparagraph. The results of simulationhave demonstrated that it has an ideal fault location precision whether in the uniformtransposed lines or non-fully transposed lines.