Research On Fault Location Of Multi-circuit Transmission Lines With Asymmetric Parameters On The Same Tower

Multi-circuit transmission lines on the same tower can not only reduce the land used for transmission line corridors and increase transmission capacity,but also have the unique advantage of coordinating the construction of power grids and local development.However,in engineering practice,there are not only complex couplings between multi-circuit transmission lines on the same tower,but also a certain asymmetry of line parameters,which will put forward higher requirements for accurate fault location of multi-circuit transmission lines on the same tower.In view of the above reasons,this thesis takes the fault location of multi-circuit transmission lines with asymmetric parameters on the same tower as the research object,which is specifically divided into the asymmetric parameter multi-circuit line traveling wave locating research under the same voltage level and the asymmetric parameter four-circuit line fault locating research based on the sequence network analysis under different voltage levels.(1)For the research on traveling wave distance measurement of multi-circuit lines on the same tower under the same voltage level,firstly,the system structure of asymmetrical parameter double-circuit line on the same tower and asymmetrical parameter four-circuit line on the same tower is deeply analyzed.Aiming at the impedance models of the above two structures in engineering practice,drawing on the traditional decoupling ideas of the six-sequence component method and the twelfth-sequence component method,various time-domain impedance decoupling matrices under the two line structures are given.Through further comparison and analysis of the modulus propagation characteristics of each decoupling matrix,a fault modulus traveling wave selection criterion suitable for traveling wave distance measurement of double-circuit lines and four-circuit lines on the same tower with asymmetric parameters is obtained.By combining the improved three-terminal traveling wave ranging principle,the unified traveling wave ranging of double-circuit line and four-circuit line on the same tower with asymmetric parameters is realized.(2)After that,the typical structure which is 4-2-2 T-type transmission line obtained by interconnecting double-circuit lines on the same tower with four-circuit lines with asymmetric parameters is further studied and a multi-modulus traveling wave ranging scheme is proposed.This scheme uses the modulus propagation characteristics of the double-circuit and four-circuit line on the same tower after decoupling asymmetric parameters,and decomposes the traveling wave ranging of the T-type line into independent multi-modulus traveling wave ranging under each single circuit in the multi-circuit line at each end.Afterwards,the non-zero value of each fault distance calculated by each multi-modulus is used to make a preliminary judgment on the fault side,and finally by comparing the arrival time of the traveling wave surge at the midpoint R of each line on the fault side,the unity of the determination of the fault branch and the fault location in the traveling wave fault location of the 4-2-2 T-type line is realized.(3)For the fault location research of the four-circuit line with asymmetric parameters on the same tower under different voltage levels,the traveling wave distance measurement scheme of the four-circuit line with asymmetric parameters on the same tower will not be suitable for the system structure due to the existence of cross-voltage levels.For this reason,the sequence network diagram method is used for fault location.First,complete decoupling between lines is achieved through two different phase mode transformation matrices.The reverse zero g0 sequence network under the two decoupling modes has the same network topology.After that,the zero sequence g0 sequence network is used to establish the fault location equation to realize the fault location of the four-circuit line across the voltage level on the same tower.A large amount of experimental simulation data shows that the two algorithms can achieve accurate ranging,and the ranging results are not affected by the operation mode of the system.