Comparative studies on the aging of thermally upgraded paper insulation in palm fatty acid ester, mineral oil, and natural ester

Tokunaga, Junko; Koide, Hidenobu; Mogami, Kenji; Hikosaka, Tomoyuki

doi:10.1109/tdei.2015.005502

Cited by 60 publications

(36 citation statements)

References 16 publications

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“…As the promising substitutes for MO, natural ester insulation oil (NEO) has several advantages of renewability and biodegradability and less flammability compared with MO [3]. In addition, NEO is claimed to delay the aging rate of insulation paper and prolong the lifetime of a transformer [4][5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Relationship between the Electrical Characteristics of Molecules and Fast Streamers in Ester Insulation Oil

Wang

Lou

et al. 2020

IJMS

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The effects of C=C, ester and β-H groups on the ionization potential (IP) and electron affinity (EA) of molecules in natural ester insulation oil were investigated by density functional theory (DFT). The major contribution to the highest occupied molecular orbital (HOMO) comes from the carbon atoms adjacent to C=C. Thus, the IPs of triglycerides decrease as the number of C=C double bonds increases. The C=C in alkanes may also lower the IP. However, the β-H in triglycerides has little effect on the IP, and C=C and β-H have only a small effect on the EAs of the triglycerides because of the major contributions of atoms near the ester group in triglycerides to the lowest unoccupied molecular orbital (LUMO). This study calculated the IPs of 53 kinds of molecules in FR3, which are significantly lower compared with those of molecules in mineral oil (MO) and trimethylolpropane triester without C=C. However, the lightning impulse breakdown voltage (LI V b ) of trimethylolpropane triester is still significantly lower than that of MO at the large gap. Therefore, the transition from slow to fast streamers under low lighting impulse voltage is determined by the ester group rather than by C=C and β-H. The ester group may attract more electrons, impacting itself more compared to alkane in MO and facilitating the transition from slow to fast streamers. Int. J. Mol. Sci. 2020, 21, 974 2 of 13The LI V b of ester insulation oil is comparable to that of MO in a quasi-uniform field [12][13][14]. However, in a non-uniform field, the LI V b of NEO is considerably lower than that of MO for large oil gaps [11,15,16], which limits the application of NEO in large power transformers. Therefore, the underlying mechanisms of this phenomenon have been receiving increasing attention. The comparison of pre-breakdown phenomenon (streamers) characteristics in MO and NEO has been reported [15,[17][18][19]. The inception voltage of streamers in NEO is lower under both polarities compared with that of MO in the non-uniform field. Streamer propagation in NEO evolves easily to fast mode, which results in its considerable low LI V b at large oil gaps [16,20]. Comparisons of discharge parameters between NEO and MO were performed by many researchers. However, the reasons why streamer propagation in NEO evolves more easily to fast mode compared with that in MO is still unknown. Therefore, it is necessary to study the relationship between the electrical characteristics of the molecules and fast streamers in insulation oils.The IP and EA of molecules are related to the propagation of streamers in insulation oils [21,22]. Thus, density functional theory (DFT) was applied to calculate the IP and EA values of the molecules; DFT is the most widely used theoretical method to simulate the properties of both organic and inorganic molecules [23]. Specifically, the C=C, ester and β-H groups are the important groups in NEO. Therefore, in this work, the effects of the C=C, ester and β-H groups on the IP and EA values of molecules in NEO were investigated. Then, compari...

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Section: Introductionmentioning

confidence: 99%

Relationship between the Electrical Characteristics of Molecules and Fast Streamers in Ester Insulation Oil

Wang

Lou

et al. 2020

IJMS

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“…22 Tokunaga et al compared the dielectric properties of aged natural esters namely, palm fatty acid ester (PFAE) and FR3 with mineral oil and found that PFAE showed the highest BDV compared with that of the remaining two dielectric uids. 23 Villarroel et al evaluated the moisture diffusion coefficient parameters for two natural esters, namely, BIOTEMP and BIOELECTRA. The results revealed the applicability of moisture dynamics during transformer operation.…”

Section: Introductionmentioning

confidence: 99%

Preparation, characterization and feasibility analysis of methyl ester of Sesbania seeds oil (MESSO) as alternate liquid dielectrics in distribution transformers

2019

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“…In Japan, the Lion Corporation developed a monoester type insulating oil called palm fatty acid ester (PFAE) [7]. The viscosity of PFAE is much less than tri-ester makes the cooling efficiency of the PFAE-immersed transformer better than that of triester oil [8]. Its viscosity is even lower than that of the convensional transformer mineral oil [9,10].…”

Section: Introductionmentioning

confidence: 99%

Properties of Thermally Aged Natural Esters Used as Insulating Liquid

Rajab¹,

Tsuchie²,

Kozako³

et al. 2018

IJEEI

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An accelerated aging test is an important test to assess a long time performance of an insulation system. This paper deals with the investigation results on thermally aged natural esters insulating liquid used for transformator. Two kinds of monoesters, palm fatty acid ester (PFAE) and stearic/oleic/linoleic acids methyl esters (M182), and one tri-ester, Envirotemp (FR3), were aged at the temperature of 120 o C for 60 days. An as-received oil was used as a sample for aging test, so that the presence of a limited amount of air, and thus oxygen, in oil sample could not be avoided. The important properties like appearance, moisture content, acid value, volume resistivity, and breakdown voltage are evaluated at each 15 days interval. Experiment on mineral oil under the same condition was also conducted for comparison. It was observed that the color of the FR3 was changed from light-green to dark-green. PFAE, M182 and mineral oils which were initially transparent became yellow-green, light yellow and brown, respectively. A sludge formation was observed in the mineral oil, whereas the increase in acidity was found in the PFAE and M182 oils. The moisture content of aged PFAE and M182 oils decreased whereas that of aged FR3 and mineral oils increased. The volume resistivity of all tested oils decreased with aging time, whereas their breakdown voltage showed a different behaviours. The breakdown voltage of M182 and mineral oils increased and decreased, respectively, whereas that of PFAE and FR3 relatively unchanged.

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Comparative studies on the aging of thermally upgraded paper insulation in palm fatty acid ester, mineral oil, and natural ester

Cited by 60 publications

References 16 publications

Relationship between the Electrical Characteristics of Molecules and Fast Streamers in Ester Insulation Oil

Relationship between the Electrical Characteristics of Molecules and Fast Streamers in Ester Insulation Oil

Preparation, characterization and feasibility analysis of methyl ester of Sesbania seeds oil (MESSO) as alternate liquid dielectrics in distribution transformers

Properties of Thermally Aged Natural Esters Used as Insulating Liquid

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