To reveal the effects of temperature and aging degree on insulation condition of transformer

and promote the application of the frequency spectrum method to detection of oil paper insulation

oil paper samples with different temperature and aging degree were prepared for frequency spectrum measurement in laboratory. The variation of the obtained spectrum curves was analyzed

and it was suggested that the parameter tanδ corresponding to different logarithmic frequency be taken as a characteristic quantity to distinguish the effects of temperature and aging degree. A real case was analyzed with the proposed method

and the results showed that temperature affects the curve in the range of logarithmic frequency values from-3 to 0

while aging degree affects the curve in the range from-3 to 2

especially in the range from-1 to 2. So the tanδ values corresponding to the logarithmic frequency values-3

-2

-1

0 and 1 were taken as the characteristic parameters for evaluation of temperature and aging degree. Furthermore

functions were deduced. The proposed method was applied to a transformer in service for measurement of temperature and aging degree

and its validity was verified.