Studying the distribution characteristics of dielectric loss and capacity incremental values for transformer oil bushings are conducive to grasp the insulation health level of running high voltage bushings. In this paper

basing on a large number of data samples of Guangzhou area

the normal distribution curves of the tanδ and capacitance variation for running high voltage bushings were obtained by comprehensively using histogram and non-parametric inspecting methods under the multiple dimensions of different rated voltage levels. The test results show that the mean and standard deviation of normal distribution curve are larger for products with early technological level and longer running time

the differences of normal distribution curves of the tanδ and capacitance variation are more obvious when the environment humidity is higher than 80%; the differences of normal distribution curves of the tanδ and capacitance variation under different environmental temperature are relatively small. It is presented that the regulations of the allowable values of tanδ and capacitance variation for running high voltage bushings should consider manufacturing technology level and the regional difference. Suggestions can be put forward that the allowable value of tanδ for running high voltage bushings with 110、220、500 k V are 0.8%

0.7%

0.6% respectively. Measures should be taken such as shortening the test cycle or using high voltage dielectric loss test to track when it is more than 0.5%; the allowable value of capacitance variation is ±3%

reasons should be find out when it is over ±2%.