“…The insulation solids usually studied include papers such as Kraft paper [10][11][12][13][14][15][16], thermally upgraded papers [9,[17][18][19], aramid paper [1,[20][21], pressboard [20,22]. The paper degradation in thermal aging studies has been evaluated through the degree of polymerization [10][11][12][18][19], the tensile strength [13][14][15][16][19][20][21][22][23], differential scanning calorimetry [24], Fourier transform infrared spectroscopy (FTIR) or energy dispersive X-ray [12] being the DP and the tensile strength the most commonly used methods to evaluate the insulating paper condition. Even though, the degradation suffered by different insulation papers immersed in biodegradable oils during thermal ageing tests has been studied, there are few works that have analyzed the effect of insulation liquids on the deterioration of other cellulosic materials such as Diamond Dotted paper (DDP).…”