Application of VG-100® as a dielectric fluid in transformers

August 2017, by Jesús Ávila Montes, Research Engineer Jr.

VG-100® is a dielectric fluid derived of natural Ester of edible seeds, formulated with a proprietary process suitable for use in transformers – both new and retrofill.

The fluid was developed by Prolec GE in 2009 as an environmentally friendly alternative to existing dielectric fluids. It is 100% natural and biodegradable, and does not contain any synthetic antioxidant, petroleum or toxic compounds. VG-100 fluid complies with international standards and requirements such as ASTM & IEEE. It is also certified by Factory Mutual (FM) and Underwriters Laboratories (UL).

To maintain the optimal properties of VG-100®, it is important to take some precautions related to its storage and handling. VG-100® can be delivered in sealed totes (drums) or tankers, shipped with a positive pressure dry nitrogen blanket to prevent fluid contamination by humidity or oxygen inside the container, or other solid or volatile material. For storage, the new fluid should be stored in areas protected from rain, direct sunlight and high temperatures. When the fluid is received, to ensure optimal characteristics and benefits, it is necessary to perform the routine tests on the fluid which are described as: Color, appearance, humidity, dielectric rupture voltage and power factor 25° and 100°.

VG-100® can be used with any equipment suitable for transformer oil, whether it is a new or old transformer filled with mineral oil (retrofill), with or without a conservator tank, provided that the oil preservation system of the equipment is properly sealed. Prior to filling the transformer, the liquid should be processed (degassed, filtered and dehumidified) to meet acceptance levels of applicable standards (ASTM D6871, IEEE C57.147 or IEC 62770). The treated fluid should be placed in the transformer tank with a previous vacuum process step. A target temperature of 80 °C will improve the impregnation process of the insulation system.

In retrofill units, it is necessary to consider the levels of humidity, oxygen and content of impurities in the insulation system of the transformer. If during the retrofill process, the fluid has been exposed or has been in contact with water or dust, it is advisable to process the oil in the same way as it is done at the factory (degassed, filtered and dehydrated). On the other hand, it is necessary to maintain the mineral oil content lower than 7%, to avoid reducing the performance benefits of VG-100®, such as flame point and level of biodegradability, among others. Once the equipment is filled with VG-100, it is necessary to perform tests of humidity, voltage at dielectric rupture, power factor at 25 ° and 100 ° C, and analysis of dissolved gases. Finally, it is important to mention that the units that underwent a retrofill process with VG-100® require the same maintenance process as for mineral oil.