The complex elastic modulus of pressboard in power transformer is closely related to the temperature anddegradation

the research on it can make great contribution to get the dynamic characteristics of power transformerwindings and the method to detect the winding mechanical condition based on vibration signal. Based on the visco-elastic theory of materials

this paper makes an accelerated aging experiment on pressboard

and then the character-istics of storage modulus and mechanical loss angle of degraded pressboard under different temperature are studiedthrough dynamic mechanical analyzer. Besides that

the relationship between complex elastic modulus

temperatureand degradation are analyzed combining with the test on degree of polymerization（DP）of pressboard. The resultsshow that the complex elastic modulus of pressboard decreases with the increase of degradation and temperature

thetangent of mechanical loss angle is below 0.055 and remains unchanged under the influence of temperature and deg-radation. The influence coefficient of complex elastic modulus decreases with the increase of degradation degree. Theresults of this paper have great guiding significance for evaluating degradation and mechanical condition of powertransformer based on vibration signals.