This article analysed the affection from the environment humidity, disturbance of intense voltage, linking mode etc on measurement result on the bases of spot fact condition, and the method to decrease or weaken the disturbance factor, which can cause the exact measurement on medium wasting factor tgδ and improve the veracity of.

Cyanate ester resin has lower dielectric loss factor,low and stable dielectric constant.

Then signification and definition of dielectric loss factor-tanδ is analyzed under harmonics exist.

An analysis has been made in this paper on the effect of space disturbance upon capacitive bushing dielectric loss factor tanδ measurement,which appears to be smaller value than the normal,sometimes even to be a negative value,in site test.

At 220 kV CVT of Line Gunan, both capacity and dielectric dissipation factor are valuably measured.

Through theoretical and practical analyses on dielectric dissipation factor measuring methods of capacitive current transformer with positive and negative connecting modes, the authors propose an onsite measuring method, which can diminish the working strength and enhance the working efficiency.

Dielectric dissipation factor (tanδ) is a key parameter in capacitive power equipment insulation on-line monitoring, which can reflect the insulation station of the capacitive equipments such as Bush and CT.