Dielectric loss on-line monitoring technology is an important means to detect bushing defects and avoid equipment accidents. However

the dielectric loss monitoring data could be affected by meteorological conditions

which might lead to false alarm. In order to reduce the false alarms caused by meteorological factors

this paper analyzes the correlation of porcelain cover oil-impregnated paper bushings’ on-line monitoring data and corresponding meteorological data

and the results show that there is a significant positive correlation between the dielectric loss and rainfall

while the correlation with the temperature and humidity of the environment is not significant; to explain these phenomenon

the author constructs the equivalent circuit model of transformer bushing.Based on the correlativity of rainfall and the dielectric loss monitoring values

three early warning strategies have been proposed to eliminate the interference of rainfall on dielectric loss monitoring data

which are the inter-phase comparison method

the comprehensive method considering meteorological condition and the time-delay method

it is verified by the monitoring data of in operation bushings that the last two methods perform well in excluding the interference caused by rainfall.