Online Transformer Dry Out System
The DRYCORE online transformer dry out system was developed to address one of the most dangerous issues in oil-filled electrical equipment — excessive moisture in insulation. It is well known that moisture, together with oxygen, accelerates paper degradation, reduces its dielectric properties and mechanical strength, triggers oxidation reactions, and contributes to the formation of new water content. Although transformer oil absorbs only a small fraction of water, over ninety-five percent remains in the solid insulation. It is there that moisture sharply accelerates aging, causes partial discharges, and increases the risk of winding-to-winding short circuits. Any temperature fluctuations in the oil — which often reach the range of 140–185 °F — enhance moisture migration and broaden its effect on insulation, potentially leading to catastrophic transformer failure.
Comparing Approaches to Transformer Drying and Evolution of Solutions
Two approaches have emerged in the industry for removing moisture from insulation. The first involves a complete shutdown of the transformer and performing deep offline drying of the active part. This method is essentially a major overhaul, requiring significant expense, extended downtime, and specialized personnel. Additionally, any disassembly of the active part carries potential risks of reduced equipment reliability and may result in undesirable consequences after re-energization.
The second approach is to use solutions like the DC-260D, which allow drying without halting operation. The DRYCORE DC-260D online transformer dry out system integrates into the oil circuit and operates autonomously, without constant involvement of maintenance personnel. The system’s pump circulates oil at approximately 0.13 gallons per minute, passing the flow through filter cartridges filled with sorbent.
The sorbent in this process:
- captures dissolved water,
- removes oil aging products,
- reduces the concentration of contaminants that accelerate insulation degradation.
The sorbent is highly adsorptive and can absorb water even at minimal concentrations. As dissolved moisture is removed from the oil, the solid insulation, following the equilibrium principle, begins to release water into the oil, which is then reabsorbed by the sorbent. This cyclical process runs continuously and ensures a stable reduction of moisture in the cellulose over several months.
Operating Principle of the DRYCORE DC-260D Online Transformer Dry Out System
The DC-260D operates on the principle that moisture migrates from areas of higher concentration to areas of lower concentration. When the sorbent removes water from the oil, the oil becomes “dry” relative to the paper and begins to draw moisture from the insulation. After returning to the drying system, this excess moisture is again adsorbed by the sorbent. With several months of continuous circulation, the solid insulation can transition from a critically moist state to a consistently dry condition, maintaining full dielectric and mechanical strength as in a new transformer.
The DC-260D design allows for quick and simple sorbent replacement. As the sorbent gradually saturates, the system is equipped with two moisture sensors — at the inlet and outlet — which allow precise determination of when maintenance is required. All control elements and terminals are located in a separate control cabinet, simplifying installation and ensuring safe operation.
The system can operate on transformers with varying oil volumes — from a few hundred to several thousand gallons — so the DC-260D configuration is selected according to the specific equipment and pump capacity. If the online transformer dry out system is applied to a new transformer, it can maintain moisture levels at or below factory standards, significantly extending insulation life. When installed on equipment already in service, its primary goal is to gradually reduce moisture content and maintain safe levels. Typically, complete insulation drying takes three months to one year, depending on transformer size, operating temperature, and initial cellulose condition.
Transformer lifespan directly depends on the quality of maintenance and the ability to preserve the original properties of solid and liquid dielectrics. The most vulnerable component is the cellulose in the windings. It is sensitive not only to water but also to oxygen, oil oxidation products, and elevated temperatures. Without controlling these factors, insulation loses electrical strength, resistance to degradation, and mechanical integrity, naturally shortening the transformer’s service life.
The DRYCORE DC-260D online transformer dry out system is a modern solution for reducing insulation moisture without shutting down equipment. It enhances oil dielectric strength, slows cellulose aging, and significantly extends transformer life. Thanks to continuous drying cycles, precise monitoring sensors, and quick-change filters, the DC-260D provides maximum protection for transformers under real operating conditions.