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DryKeep is an on-line molecular sieve, stationary, continuous water removal system. It is capable of reducing water levels from 50 ppm to less than 10 ppm in transformer oils. The continuous on-line removal of water from the transformer oil also ensures the removal of the moisture and fibers in the solid insulation. The diffusion of the moisture from the solid insulation to the oil maintains the associated equilibrium as water is removed from the oil. This process not only reduces the paper aging, but will improve the dielectric strength of the insulation and increase reliability. It enables transformers to be run on higher load cycles with greatly reduced risk of failure. The increased plant utilization will allow capital expenditure to be deferred.

In free breathing transformers water can not only enter the insulation material through the natural expansion and contraction of oil as the temperature cycles, but water is a by-product of the degradation of the long chain hydrocarbon glucose molecule as the result of thermal and electrical stress. Excessive moisture will saturate the insulation and increase its conductivity. Higher temperatures increase the risk of bubble evolution and partial discharge. It should be noted that the deterioration of paper is directly proportional to its water content.

The system was originally intended to be installed on a properly dried out transformer to maintain this ideal state throughout its service life. But, due to the effective drying capabilities, the DryKeep system was soon installed on older wet transformers. It was found to be an effective moisture management tool.

DryKeep can benefit power transformers in various ways:

  • New Transformers-A DryKeep installed on a new or recently reconditioned transformer will maintain the moisture content at the 0.5% factory level as it removes small quantities of water. It may more than double the design life of this expensive asset for a fraction of the cost of a new transformer.

  • Older In-service Transformers-DryKeep will extend the service life of the transformer by many years by slowly reducing the water content of the paper and maintaining it at a predetermined level. If re-clamping the windings is possible to perform on site, reduce the moisture content to the factory level of 0.5%. If re-clamping is not possible, we recommend not drying out below 1.3%.DryKeep will predetermine the amount of moisture in the paper before installation and estimate the number of cylinder changes required. The amount of time required to dry out the unit will vary with the size, moisture content and operational temperature variation. The time period is typically between 10 and 24 months.

  • Out of Service Transformers-Off-line transformers should be kept free from moisture formed through condensation during normal ambient temperature cycles. When the transformer is returned to service, the oil must be dry and capable of handling the electrical stresses of loading. DryKeep is an obvious solution.