A comparison of bubble evolution temperature in aramid and cellulose paper

Abstract

The paper deals with the problem of the bubble effect in transformer winding insulation. The bubble effect should be understood as the release of water vapor from insulation. The main goal of the research was to compare the initiation temperature of bubble evolution in aramid and cellulose paper depending on the water content. Cellulose and aramid paper samples of different water content were prepared for the research study. The obtained results confirmed that aramid paper is less hygroscopic than cellulose paper. It was also proven that the initiation temperature of bubble evolution is lower for aramid paper than for cellulose paper with the same water content. However, the initiation temperature of bubble evolution is very similar for aramid and cellulose paper conditioned at the same relative humidity.

Analysing the power transformer temperature limitation for avoidance of bubble formation

“…Across systems, however, the temperature dependence on energy input differs, and as the energy inputs are not stated, a comparison between systems is not possible. [12,18,[35][36][37] Przybylek [39] 144.6 125.8 174.0 147.9 Koch & Tenbohlen [18] 156.3 180.7 174.8 207.2 Perkasa [36] 140.0 146.7 161.4 166.0…”

“…Table 2 summarises the BIT at 2% and at 1% moisture from both studies. There is a divergence in the results, however, with [39] witnessing a decrease in BIT for Aramid, whereas [18] see a large increase in BIT for TUP. While it is not necessarily expected that the two different materials (Aramid and TUP) would perform similarly compared to standard Kraft paper, it clearly indicates that more investigation is needed into alternative solid insulation material in order to establish the impact of material selection on BIT and the reasons behind deviations in BIT.…”

“…Comparison of BIT at different rates of change of temperature based on data from [18,35,39] i. Introduction of condition-based limitations appears to be necessary.…”

“…There are two studies found which have looked at alternative solid insulation, [18, 39]. Reference [39] looked at Aramid insulation, and [18] used TUP (with no further detail, e.g. brand or N 2 content, provided).…”

Analysis of High-Frequency Dispersion Characteristics of Capacitance and Loss Factor of Aramid Paper Impregnated with Various Dielectric Liquids

“…It is probable that the main cause of a possible failure of a high-power transformer with aramid insulation is damage to the solid insulation caused by aging. Therefore, apart from assessing the degree of moisture, it is important to develop a method of non-invasive assessment of the degree of thermal degradation [6,[8][9][10][11][12].…”