Application of Paraffinic Insulating Oil for Large-scale Transformers

• Published in: Journal of The Japan Petroleum Institute Vol. 29; no. 2; pp. 122 - 130
• Main Authors: MASUNAGA, Midori, MORI, Sadao, YOROZUYA, Tsuruo, TSUKIOKA, Hideo, MIYAMOTO, Teruo, ISE, Junichi
• Format: Journal Article
• Language: English
• Published: The Japan Petroleum Institute 1986
• Subjects: Alkylbenzene; Charging tendency; Naphthenic oil; Paraffinic oil; Pour point depressant
• ISSN: 0582-4664
• DOI: 10.1627/jpi1958.29.122

Naphthenic crudes regularly used to manufacture insulating oils are rapidly being depleted. More plentiful paraffinic crudes should be substituted to supply the world's future needs for electrical equipment. Research on paraffinic insulating olis has been conducted throughout the world, although such oils have seen only in the smaller service in Canada, Europe, Japan and few other countries. However, not so much information has been developed about the suitability of paraffinic insulating oils containing pour point depressants in modern high voltage transformers. Recent trends in power transformer design increase in both capacity and voltage with a reduction in overall size. These increased requirements for higher reliable insulation of power transformers urge the need to improve the quality of insulating oils. For example, the currently limited oxidation characteristics of oil need be more stable, to suppress the static electrification of oil caused by oil flow. This study was undertaken in an attempt to evaluate the effect of transformer oils on the degradation of paper. Further, the tendencies of gas evolution of oils under degradation and high electric stress are also studied. Additionally, dielectric tests of model insulation systems were studied. Three paraffinic oils shown in Table 1, were examined. Two commercially available pour point depressants, one-an alkylated polystyrene, the other-ethylene propylene copolymer were used. As a comparative oil, a blend of naphthenic oil and alkylbenzene was used. There appeared to be little difference among types and amounts of combustible gases produced from either a paraffinic or a naphthenic oil when tested by high voltage oil gap tests or thermal degradations (Table 3, Figs. 9 and 10). In other studies, such as dielectric tests of papers and model insulation systems, there are essentially no differences in charging tendency for the two types of oils tested under the degradation test (Figs. 12-18, Tables 4-8). It was concluded that it might be possible to replace naphthenic oils with paraffinic oils for large power transformers in future.