Research on Electric Unbalance Degree and Conductor Transposition of 1000 kV Double-Circuit Transmission Line on the Same Tower

Electric unbalance degree is an important index to measure the performance of transmission lines and power quality.Taking the 1 000 kV double-circuit transmission line on the same tower from Huainan to Shanghai for example,by means of EMTP and Matlab the electric unbalance degree of the transmission line under various operation conditions is simulated and calculated.According to the calculation results the electric unbalance degree and conductor transposition of UHV double-circuit transmission line are researched.Following conclusions are obtained:the unbalance degree of double-circuit transmission line on the same tower can be obviously reduced by negative phase sequence arrangement of conductors and it is recommended that for the 1 000 kV UHV transmission line adopting negative phase sequence arrangement the conductor transposition interval should be 200 m;the unbalance degree of the double-circuit transmission line transposed in the same direction is obviously less than that transposed in reverse direction;for 1 000 kV double-circuit transmission line on the same tower from Huainan to Shanghai,it is recommended to adopt the negative phase sequence conductor arrangement to full length of the double-circuit transmission line,and the demand to unbalance degree can be met by one full transposition in the same direction of the 1 000 kV double-circuit transmission line within its section from Huainan to Wannan.