In recent years, environmental concerns have been raised on the use of poorly biodegradable fluids in electrical apparatus in regions where spills from leaks and equipment failure could contaminate the surroundings. The vegetable insulation oils are highly biodegradable, have negligible effect on the environment, human health and ecosystem. Therefore, to assure their safe use in electrical power systems, it may require some processing and modification to improve some of their physical, chemical, thermal and electrical properties. This paper provides a comparative results of the electrical breakdown properties of several vegetable insulation oils and mineral oil to use as dielectric fluid in environmental-friendly pole transformer. Also, the electrical breakdown property of the Nomex and kraft insulation papers in vegetable insulation oil is examined.