COMPARISON BETWEEN DRY TYPE AND LIQUID FILLED TRANSFORMERS
What Is The Difference Between Dry Type and Liquid Filled Transformers?
The advantages and disadvantages of dry-type transformers versus liquid-filled units depend upon the application. Dry-type transformers can usually be located closer to the load, resulting in cost savings because of shorter cable runs and lower electrical losses.
A liquid-filled transformer, on the other hand, may require special construction features for the room in which it will be placed because of fire safety considerations. This may dictate a location some distance from the load.
In addition, periodic testing must be conducted on the fluid to determine its dielectric strength, water content, dissolved gases, and other parameters.
In some applications, there is no option to the use of liquid-filled transformers; dry-types are limited in size and voltage handling capability. Liquid-filled types are available in almost limitless kVA and voltage ratings.
Also, if requirements call for a transformer to be located outdoors, it may be less expensive to purchase a liquid filled unit. With oil as the liquid, the cost would be lower than for a dry-type of equivalent rating; with low-firepoint fluids, the cost would probably be comparable to a dry-type.
For liquid-filled transformers, the main cooling/insulating mediums used today are mineral oil, high-molecular-weight hydrocarbon, and silicone fluid. If a leak occurs in the transformer tank, fire safety becomes an important issue.
Because of hazards associated with tank rupture and the possible ignition of the dielectric, a thorough analysis covering fire safety and the possible effects on the environment should be carried out well in advance of device installation.
Some materials are covered under the Federal Resource Conservation and Recovery Act and the Clean Water Act, including requirements for:
• Special handling
• Spill reporting
• Disposal procedures
• Record-keeping
These considerations can have an effect on installation costs, long-term operating expenses, and maintenance procedures.
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