The clearance of the 500 kV AC-DC mixed voltage lines on the same tower is narrow and the arrangement of the wires is complicated. In order to determine the maximum electric field strength on body surface and the entering path to equipotential level for the workers

who are engaged for live operation on 500 kV AC-DC mixed-voltage double-circuit transmission line

the straight-line tower for the AC-DC mixed-voltage double-circuit transmission line of the Zhang-Bei flexible 500 kV DC transmission line project is taken as an example to establish model in the finite element simulation software Ansys. The body surface electric field strengths of a worker entering into all possible equipotential paths of the AC circuit of the mixed-voltage double-circuit line are calculated and analyzed in the typical working conditions of middle phase

side phase

and DC circuit

and then the optimum path for entering equipotential level is determined according to the maximum electric field strength distribution on body surface. The results show that the maximum values of the body surface electric field strength at the middle-phase and side-phase wires in the AC circuit tower window are 1 875 and 1 032 kV/m

respectively

and the maximum value at the DC pole wires is1 110 kV/m. The average body surface electric field strength is the largest during the whole process of the worker entering the equipotential level vertically. For the AC-DC mixed-voltage double-circuit line on the same tower

the entering angle has an important influence on the electric field distribution on human body surface. The optimal angles entering the equipotential level of middle phase and side phase of the wires in the AC cup type tower are 45° and50°

respectively

while the optimal angle entering the equipotential path of the DC pole wires is 30°.