Research On Physical-Chemical And Electric Properties Of Vegetable Oil Based Dielectric Liquid

Mineral oil is an excellent type of dielectric liquid with high coolant capability and low cost, it has played important roles as both insulators and coolant liquid in oil-immersed high voltage equipment more than a century. But its flash point is too low to satisfy the requirement of fireproofing. It is poorly biodegradable as well and may contaminate soil, waterways, and resident conditions when serious oil spill or leakage occurs. At present, the high cost is restricting the widely using of mineral oil based high burning point oil and flame resistance oil, such asαfluid,βfluid, silicone oil and Midel 7131. So, it is a topic to researching a new dielectric liquid with high burning point, high permittivity and high biodegradability.Researches on using vegetable oil as dielectric liquid began at the same time as mineral oil. Due to the fact that vegetable oil has a high pour point and viscosity, it is only used as impregnant in capacitors. From 1990s, the researches of using vegetable oil as dielectric liquid have been developed again. Vegetable oil, extracted from crude seed oil, is fully biodegradable. Its flash point exceeds 300℃. Nowaday, the output and quality of oil crops are improved by using gene techniques, and the reserves of mineral oil became decreased, so vegetable oil could be the green substitute as mineral oil.This paper explored the methods how to refined the vegetable oil to dielectric liquid, studied the similarity and otherness on macrocosm representation between mineral oil and vegetable oil from microcosmic view, researched the physical, chemical and electrical properties of vegetable oil, and studied the oxidation process and biodegradability of vegetable oil. Furthermore, this paper researched the accelerated aging lifetime of vegetable oil-paper under electrical stress, discussed dielectric performance of vegetable oil-paper. This paper is the groundwork of using vegetable oil as dielectric liquid, and the production of the paper filled up the blank of vegetable insulating oil studies in domestic study.The investigation shows, vegetable oil high in oleic acid is the best choice as base oil. Controlling the dominating testing conditions in vegetable oil refined processes, and using repeated refined method, the acid value of vegetable oil can be limited under 0.03mgKOH·g-1. After refining, the physical, chemical and electrical properties of vegetable oil met the requirements of standard GB2536-90 . Usually, high flash point oil has high kinematic viscosity. The kinematic viscosity of vegetable...