Methods for improving the workability of natural ester insulating oils in power transformer applications: A review

Ghani, Sulaiman Ab; Muhamad, Nor Asiah; Noorden, Zulkarnain Ahmad; Zainuddin, Hidayat; Bakar, Norazhar Abu; Talib, Mohd Aizam

doi:10.1016/j.epsr.2017.10.008

Cited by 85 publications

(36 citation statements)

References 56 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Triglycerides are the main constituents of NEO. Figure 2(a) shows the molecular geometry of triglycerides with β-H, which significantly lowers the oxidation stability of NEO [3,31,32]. The D, D ' and D" in the molecule represent the fatty acids, which always contain C=C.…”

Section: Methodsmentioning

confidence: 99%

“…To improve the safety and reduce the environmental impact of the transformer, alternative insulation oils are demanded [2]. 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%

See 1 more Smart Citation

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

Wang

Lou

et al. 2020

IJMS

View full text Add to dashboard Cite

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...

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Wang

Lou

et al. 2020

IJMS

View full text Add to dashboard Cite

show abstract

“…The percentage of FFA content is an important specification that affects the quality of palm oil in the storage, production and marketing stages [9]. This will enable NEI to be used in the distribution transformer [10]. An original NEI also has a higher total acid number (TAN) values which normally above than 0.3 mg KOH/g [11].…”

Section: Introductionmentioning

confidence: 99%

The Experimental Study on the Potential of Waste Cooking Oil as a New Transformer Insulating Oil

Deraman¹,

Bakar²,

Aziz³

et al. 2020

ARFMTS

Self Cite

View full text Add to dashboard Cite

Power transformers use mineral oil as an insulating liquid due to its outstanding dielectric properties. The poor biodegradability and toxicity of mineral oil have increased the interest in the use of a more environmentally friendly product such as ester-based oil. Generally, natural ester insulating oils (NEI) have a higher flash point and breakdown voltage compared to existing mineral oils. However, the higher price of NEI is the main obstacle to widely applied in power transformers. Therefore, alternative cheaper feedstock processing is required. This paper proposed waste cooking oil (WCO) as a potential alternative to the existing transformer insulating oil. The used of WCO promotes the optimal consumption of plant-based resources and more efficient waste management. Transesterification method is performed to remove the free fatty acids in the WCO and reduce the viscosity. The transesterification process is based on the chemical modification reaction between WCO, methyl alcohol (methanol) and sodium hydroxide (NaOH) catalyst lye that produces waste cooking oil methyl ester (WCOME). Chemical and electrical properties i.e. water content, acidity and breakdown voltage of the developed WCOME are compared with the existing WCO according to IEEE Guide for Acceptance and Maintenance of Natural Ester Fluids in Transformers (IEEE C57.147).

show abstract

“…However, MOs can cause serious problems due to their low flash point which have caused several fire accidents. The poor degradation ability of MO causes disposal problems against environmental laws and regulations in many countries [2]. Therefore, natural ester insulation oils (NEOs) as promising substitutes for MO in transformers have been received increasing attention due to the advantages of renewability and biodegradability and less flammability compared with MOs [2].…”

Section: Introductionmentioning

confidence: 99%

“…The poor degradation ability of MO causes disposal problems against environmental laws and regulations in many countries [2]. Therefore, natural ester insulation oils (NEOs) as promising substitutes for MO in transformers have been received increasing attention due to the advantages of renewability and biodegradability and less flammability compared with MOs [2]. The sealed tube thermal aging tests of insulation papers in NEOs have been performed at 90 • − 180 • C [3]- [6].…”

Section: Introductionmentioning

confidence: 99%

Thermal Aging Characteristics of Newly Synthesized Triester Insulation Oil

Wang

Zhao

et al. 2019

IEEE Access

View full text Add to dashboard Cite

High-stability triester insulation oil derived from the trimethylolpropane esters (TME) was synthesized by esterifying saturated fatty acids and trimethylolpropane (TMP). The TME oil shows higher AC breakdown voltage (V b , 72.6 kV/2.5 mm) than that of FR3 (65 kV/2.5 mm). TME oil is readily biodegradable whose biodegradation is 82.2% after 28 days. Pressurized differential scanning calorimetry (PDSC) was applied to measure oxidation onset temperature (OOT) of TME oil for initial evaluating the oxidation stability. Due to the elimination of the carbon-carbon double bonds and β-H, the OOT of the TME oil without antioxidants is approximately 25 • C higher than that of FR3. To evaluate the realistic performance of the TME oil, the effect of transformer materials on the aging behavior was investigated. The effect of transformer materials on the thermal aging of TME oil and mineral oil (MO) is less than that of FR3. Although the moisture content and acid value in TME oil induced by aging are higher than those in MO. These acids and moisture do not cause obvious degradation of breakdown voltage and dielectric loss factor, which may be attributed to the high moisture solubility in it. INDEX TERMS Triester, physicochemical and electrical properties, insulation oil, thermal aging, breakdown voltage.

show abstract

Methods for improving the workability of natural ester insulating oils in power transformer applications: A review

Cited by 85 publications

References 56 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

The Experimental Study on the Potential of Waste Cooking Oil as a New Transformer Insulating Oil

Thermal Aging Characteristics of Newly Synthesized Triester Insulation Oil

Contact Info

Product

Resources

About