Analysis On Electromagnetic Environment Of Mixed Voltage Four-Circuit Transmission Lines On Same Tower

The technology of multi-circuit transmission lines (MCTL) on same tower is one novel transmitting technology, which can obviously decrease the route way resource, and the transmission capacity per area is increased prominently. It is the popular over-head transmitting technology both in China and overseas, which has good economic benefit and application value. But comparing to a single-circuit transmission lines, its electromagnetic environment problem is one of the keys which affect the feasibility of MCTL on same tower, so it's important to analyze the electromagnetic environment.This paper analyzes the electromagnetic environment generated by the mixed voltage four-circuit transmission lines on same tower. The main work reads as follow:First of all, the paper designs the tower types and the phase sequences of the mixed voltage four-circuit transmission lines on same tower. The voltage levels are 500kV and 220kV mixed voltage.Secondly, this paper uses the software of ANSYS and MATLAB to calculate the electric field intensity and magnetic field intensity generated by transmission lines in different phase sequences of different tower types. From the simulating results, we can get that the negative phase sequence of vertical tower has the smallest electromagnetic field intensity; the third phase line sequence of d-type tower is the second choice in electromagnetic field intensity aspect.At last, this paper uses the software MATLAB to calculate the radio interference field intensity and audible noise generated by transmission lines in different phase sequences of different tower types. From the simulating results, we can get that the third phase sequence of e-type tower has the smallest radio interference field intensity. The second phase sequence of vertical tower has the smallest audible noise.In extra-high voltage transmission lines, the audible noise can completely satisfy to noise standards. When the primary consideration criteria can ignore the audible noise, the fourth phase sequence of vertical tower is the best tower and best phase sequence. The second choice is the third phase line sequence of d-type tower. This proves the theory that the negative phase sequence is a kind of effective method of decreasing electromagnetic field intensity, can not only be used for the double-circuit transmission lines on same tower, can also be used in MCTL on same tower. This can provide theoretic reference for construction of transmission lines.