Liquid-Filled Transformer
In this type of transformer, the windings and core are totally immersed in a liquid contained in the transformer tank. The tank is equipped with cooling fins for circulation of the transformer liquid. The transformer liquid provides an insulating medium for the coils as well as for dissipation of heat. Two liquids have been used extensively in the past for transformers: mineral oils and polychlorinated biphenyls (PCB), commonly known as askarel. Askarel was extensively used in transformers for indoor applications because it is a nonflammable synthetic insulating fluid. Askarel is a nonbiodegradable and toxic. Environmental Protection Agency (EPA) banned the use of askeral in transformers and other electrical equipment, and its availability for reuse or for use in new applications is almost nonexistent. Newer fluids have been introduced, such as silicone, RTemp, Wecosal, and Alpha 1 for replacement of askarel. Others are still in developmental stages. Regardless of what new fluids come on the market for transformer applications, they would still have to be maintained and tested to assure transformer integrity.
Several cooling methods are used for liquid-filled transformers.
Self-cooled: A self-cooled transformer uses the natural circulation of the insulating liquid. Heat in the transformer tank is dissipated by convection currents set up in the liquid, which circulates through the tank and cooling fins. The cooling class designation for this transformer is oil natural, air natural OA.
Forced air cooled: In this type of transformer, air is forced over the cooling surface of the tank to supplement the self-cooled rating. The supplemental air is provided by fans that are mounted on the transformer tank and which can be
Liquid-Filled Transformer
In this type of transformer, the windings and core are totally immersed in a liquid contained in the transformer tank. The tank is equipped with cooling fins for circulation of the transformer liquid. The transformer liquid provides an insulating medium for the coils as well as for dissipation of heat. Two liquids have been used extensively in the past for transformers: mineral oils and polychlorinated biphenyls (PCB), commonly known as askarel. Askarel was extensively used in transformers for indoor applications because it is a nonflammable synthetic insulating fluid. Askarel is a nonbiodegradable and toxic. Environmental Protection Agency (EPA) banned the use of askeral in transformers and other electrical equipment, and its availability for reuse or for use in new applications is almost nonexistent. Newer fluids have been introduced, such as silicone, RTemp, Wecosal, and Alpha 1 for replacement of askarel. Others are still in developmental stages. Regardless of what new fluids come on the market for transformer applications, they would still have to be maintained and tested to assure transformer integrity.
Several cooling methods are used for liquid-filled transformers.
Self-cooled: A self-cooled transformer uses the natural circulation of the insulating liquid. Heat in the transformer tank is dissipated by convection currents set up in the liquid, which circulates through the tank and cooling fins. The cooling class designation for this transformer is oil natural, air natural OA.
Forced air cooled: In this type of transformer, air is forced over the cooling surface of the tank to supplement the self-cooled rating. The supplemental air is provided by fans that are mounted on the transformer tank and which can be
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