Thermal aging properties of BIOTEMP oil with controlled air

The accelerated thermal aging test with controlled air was performed at 170°C for 216 hours, using the oil-paper insulation samples which were composed of BIOTEMP oil, NOMEX paper and pressboard. Some aging indicators including degree of polymerization of pressboard, dielectric strength of oil, acid value of oil, furfural concentration of oil, and water content, etc, were measured and recorded during the aging process. The variation of the parameters against the aging time, the correlation among these parameters and reasons for them are analyzed systematically. The results show that: with the increase of aging time, the breakdown voltage of oil decreases gradually, the acid value of oil increases, the moisture content of oil and paper first increase and then decrease but the moisture content of pressboard fluctuates; the logarithm of the furfural has a good linear relationship with the DP.