Aging of Kraft paper in natural ester dielectric fluid

Abstract

Kraft transformer insulation paper aged in, natural ester (vegetable oil) dielecvic fluid was compared to identical paper aged in conventional transformer mineral oil. Sealed steel aging tubes containing copper, aluminum, Kraft paper, and dielectric fluid (mineral oil and natural ester) were aged at 150°C for 500, 1000, 2000, and 4000 hours. The extent of paper degradation after aging was determined using paper tensile strength, paper degree of polymerization, and furanic compounds in the aged fluid. Water contents of fluids and paper were compared. Paper aged in conventional transformer oil degraded at a significantly faster rate than in natural ester dielectric fluid. Paper in mineral oil reached three criteria for EEE end-of-life (50% retained tensile strength, 25% retained tensile strength, and degree of polymerization of 200) within the first 1000 hours. After 4000 hours of aging, paper in natural ester did not degrade to any of the E E E end-of-life criteria. At 4,000 hours, the paper aged in natural ester,retained about 55% of the original tensile strength and a degree of polymerization of about 280. Paper aged in conventional transformer oil degraded to the same values in about 315 and 390 hours, respectivelyan order of magnitude faster. The reduced paper-aging rate in natural ester is primarily attributed to the fluid maintaining the paper in a very dry state. ' Whiteley Ltd. Grade K 0.255" presspaper ' Cooper Power Systems Tranelec@ inhibited insulating mineral oil and Envirotemp@ FR3-natural ester dielectric fluid 0-7803-7350-2/0U$17,00 0.2002 IEEE

Study on the Effects of Thermal Aging on Insulating Paper for High Voltage Transformer Composite with Natural Ester from Palm Oil Using Fourier Transform Infrared Spectroscopy (FTIR) and Energy Dispersive X-ray Spectroscopy (EDS)

“…Thermal aging in sealed systems was chosen based on the recommendation of the IEEE loading guide for modern sealed transformers [22]. All the sealed glass bottles were put in a different aging oven and heated to 120 • C, while the other oven was heated to 150 • C for 336, 672 and 1008 h. The 150 • C temperature level selected from the reference published in IEEE by McShane, et al [13], while the 120 • C temperature level is a hot spot temperature according to the IEEE [23]. Samples and their treatments are shown in Table 1.…”

Fourier Transform Infrared (FTIR) Spectroscopy Analysis of Transformer Paper in Mineral Oil-Paper Composite Insulation under Accelerated Thermal Aging

“…All of the sealed glass bottles were placed in two different ovens for aging and heated to 120 °C and 150 °C, respectively, for a certain period of time. Samples were taken out of the ovens at regular intervals: 336, 672, and 1008 h. Aging at a temperature of 150 °C was selected according to a reference published in IEEE by Mc Shane et al [23], while aging at a temperature of 120 °C is a hot spot temperature according to the IEEE [24]. A list of samples is shown in Table 1.…”

Suitability of Palm Based Oil as Dielectric Insulating Fluid in Transformers

“…The high flash and fire points of vegetable oil ensure more in-service operation safety than mineral oil [5]. Moreover, vegetable oil such as natural ester could also slow down the ageing rate of cellulose insulation through water scavenging and hydrolytic protection mechanisms [2][3][4]12].…”

“…Vegetable oil such as natural ester or synthetic ester is among the alternative fluids being considered. For years, various research works were carried out on different aspects such as on the safety / environmental, ageing and electrical performances of the vegetable oil [2][3][4][5][6][7][8][9][10][11][12]. Vegetable oil such as natural ester was also successfully applied in-service where it was used from small to medium transformers up to a voltage level of 66 kV [11].…”