The thunderclouds activities encountered frequently by the transmission lines in operation affect electric field environment. The geometric diameter of the thunderclouds can reach tens of kilometers and have continuous movement characteristics. The existed research still lacks the electric field analysis method transmission line -nearby building structure under background of thunderclouds and

at the same time

the existing experimental research lacks the scale selection basis of thunderclouds-transmission line-nearby building overall model. Therefore

the extra-high voltage (EHV) transmission lines and the nearby buildings in case of thunderclouds is taken as the object and on the basis of the three-layer charge structure

the analysis model of the thunderclouds-transmission lines- nearby building is proposed to analyze electric field characteristic at observation point of the transmission line and the nearby building under the thunderclouds activity and discuss the overall influence of the scale ratio of the experiment model of thunderclouds-transmission lines-buildings. It is concluded through the research that the peak of the electric field of the observation point on the building due to active thunderclouds increases by 47%. The DC component and power frequency component of the electric field increases by 40% and 200%

respectively. The electrical field deviation is lowest at the ratio of 1∶40 for the experiment scale model among the five ratios.