Research Of Fault Line Detection Method For Four-circuit Transmission Lines On The Same Tower

Four-circuit transmission lines on the same tower have the characters of taking asmall footprint, sending large capacitance, fast construction and high economicefficiency. As an important part of our ultra/UHV backbone grid, it will undertake theimportant work of the transmission of the electricity. However, due to the specificityand complexity of the structure and parameters of the lines, there are differentinductance and capacitance between lines. In addition to one line failure, due to theshort distance between the four loops, the failure between multi-loop cross-line mayoccur. The types of the failure are various and the characteristics of the failure arecomplex. After the failure, it is the premise of Relay’s correct work to make sure theposition of the failure. Therefore, there is an important theoretical and practicalsignificance to study the method of the same pole multi-loop fault line selection.On the basis of studying the parameters characteristics of same pole and four-loopfault line, we can use the double-circuit line impedance matrix which can decouplingmatrix completely to transform twelve current phasors to one set of double backpositive,negative and zero sequence current. Through the analysis to the failuresequence network, we can determine the relationship of the currents between thefailure place and protection installed position, as the theoretical basis of the analysisof the four-back line fault of the same pole.Then the characteristics of the phase and amplitude of the current within thefailure of four line at the same pole are analyzed. When the fault is located in differentback lines, three pairs anti-sequence current phase relationship are different. On thisbasis, we come up with the method of using three anti-sequence current phaserelationship to choose the fault line; When the fault is located between two differentline, double lines of same sequence and anti-sequence has different characteristics,and on this basis, we select the method to choose the fault line using the phase andamplitude relationship between double lines of the same sequence as well as thedifferent sequence.We build a four-loop simulation model on PSCAD to simulate and emulatedifferent failures of one line and two-loop lines, whose result proves that the theorywe have come up with is correct. At last, a briefly describe the outcome of this study is presented, with theinadequacies of this article and a list of further research directions.