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 transformer insulation. It is well known that moisture, along with oxygen, accelerates paper degradation, reduces its dielectric properties and mechanical strength, triggers oxidation reactions, and contributes to the formation of additional water. 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 turn-to-turn short circuits. Any temperature fluctuations in the oil — which often reach 140–185 °F — enhance moisture migration and broaden its impact on insulation, potentially leading to catastrophic transformer failure.
Comparing Transformer Dry Out Techniques and Developing Solutions
Two techniques have emerged in the industry for removing moisture from insulation. The first involves complete shutdown of the transformer and deep offline drying of the active part. In essence, this method constitutes a major overhaul, requiring significant expense, extended downtime, and specialized personnel. Furthermore, any disassembly of the active part carries potential risks of reduced equipment reliability and may result in undesirable consequences after re-energization.
Another technique involves the use of technological solutions such as the DC-260D, which allow drying without interrupting transformer operation. The DRYCORE DC-260D online transformer dry out system integrates into the oil circuit and operates continuously, 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.
In this process, the sorbent:
- captures dissolved water;
- removes oil aging products;
- reduces the concentration of contaminants that accelerate insulation degradation.
The sorbent is highly adsorptive and can adsorb water even at very low concentrations. As dissolved moisture is removed from the oil, the solid insulation begins to release water into the oil according to the equilibrium principle; the water is then re-adsorbed 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 online transformer dryout system 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 dielectric and mechanical strength comparable to that of a new transformer.
The DC-260D design allows for quick and simple sorbent replacement. As the sorbent gradually becomes saturated, the system is equipped with two moisture sensors — at the inlet and outlet — allowing precise determination of when maintenance is required. All control components 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 the service life of insulation. When installed on equipment already in service, its primary goal is to gradually reduce moisture content and maintain safe levels. Complete drying of transformer insulation 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 dielectric solids and liquids. The most vulnerable component is the cellulose in the transformer windings. It is sensitive not only to water, but also to oxygen, oil oxidation products, and elevated temperatures. Without controlling these factors, transformer insulation loses electrical strength, resistance to degradation, and mechanical integrity, which naturally shortens the transformer service life.
The DRYCORE DC-260D online transformer dry out system is a modern solution for reducing insulation moisture without shutting down the equipment. It enhances dielectric strength of oil, decelerates cellulose aging, and significantly extends transformer service life. Owing to continuous drying cycles, precise monitoring sensors, and quick-change filters, the DC-260D provides maximum protection for transformers under real operating conditions.