The electromagnetic coupling and electrostatic induction action is very strong due to the small spacing

multiple circuits and large voltage level differences of the mixed-voltage and four-circuit transmission lines on the same tower. In order to effectively reduce the level of induced electricity

the phase sequence

layout and type selection of earthing switch of the transmission line shall be reasonably designed. In this paper

a project of a 500 kV/220 kV mixed-voltage and four-circuit power transmission lines on the same tower is taken as the research object

the simulation model based on the ATP-EMTP software is set up

and the influence of the 500 kV double-circuit lines on the induced voltage and induced current of 220 kV double-circuit lines on the same tower under the interactions of such multiple factors as the operation mode

power flow of line

and phase sequence arrangement change is studied. Based on the flexible current sensing technology

the induced current of the 220 kV double-circuit lines is actually measured on site

and the accuracy of the calculation model is further analyzed and verified. The research results show that the magnitude of the power flow of 500 kV double circuit is positively correlated with the electromagnetic induced current of the 220 kV double-circuit lines on the same tower

but the influence on the static inductance level is less. In case of using the arrangement of inverse phase sequence of 500 kV double-circuit of the mixed-voltage and four-circuit on the same tower

the induced current level of the 220 kV double-circuit will be reduced significantly. While

in case of connection of the ground wire in sections

the electromagnetic induction current near the middle of the four-circuits of mixed-voltage is smaller and the junction of the two ends is larger. It has been verified by measurement that the the theoretical calculation value of the induced electricity is slighter larger than the actually measure value and this is related to the selected parameters of the simulation calculation

which reserves sufficient safety mar-gin for the type selection of earthing switch. A technical solution of changing the switching of induction voltage of the open type earthing switch is proposed to solve the problem of insufficient switching induced electricity of the earthing switch of GIS. The research results can provide important basis for the design of the mixed voltage multiple circuit transmission on the same tower

type selection of the grounding wire and the insufficient of switching induced electricity ability of the earthing switch.