Transformer Drying Process with Low Frequency Heating

Moisture's interaction with electrical devices poses a significant threat, and the moisture within a transformer's paper insulation is a concealed danger. Experts in the field are well-aware that elevated moisture content in transformer paper insulation can result in complications like depolymerization, diminished dielectric strength, and the looming danger of bubble generation. These aren't just hypothetical risks; they can considerably curtail a transformer's operational life.

Hidden Moisture: What Amount of Water is Transformer Holding?

At their core, transformers are marvels of electrical engineering. However, like many intricate devices, they aren't immune to the subtle intrusion of water. So, where does this moisture intrusion stem from? Predominantly, the culprit is the cellulose-based solid insulation inherent in power transformers, that absorbs moisture from air. This material's hygroscopic character means it can soak up to 5% of its weight during usage. Such absorption isn't just a minor inconvenience; it has grave implications. Excessive moisture has the potential to instigate dielectric failure and accelerate the deterioration of the cellulose-based paper insulation.

Delving into the manufacturing dynamics, transformers are subjected to a rigorous drying phase. Here, the entire active section endures either a vapor phase or an analogous drying procedure to eliminate as much moisture as feasible. Once extracted from this drying phase, there's an urgent flurry of activity: technicians fine-tune mechanical elements, secure the windings, and infuse the transformer tank with insulating oil. The objective? Curtail any potential for moisture to seep back in, but it can find the ways, especially during the operation or repair.

While the insulating oil itself harbors some moisture, the real reservoir is the solid insulation. To illustrate, imagine a standard-sized power transformer. If its solid insulation hosts 0.5% moisture by its weight during tanking and the oil comprises 20 ppm (even though oil typically undergoes purification), there’s a significant contrast: roughly 20 liters of water in the insulation against a mere 560 ml in the oil. To put this in everyday terms: it's like contrasting the water in a full cooler dispenser to that in a modest water bottle.

Traditional Drying Strategies

Faced with the issue of moisture in transformer isolation, numerous strategies were conceived, each with its unique merits and applications:

Hot Oil Spraying:

Principle: This method is predicated on the use of high-temperature oil. When sprayed onto transformer components, the elevated temperature of the oil facilitates the vaporization of moisture.

Advantages: The method is direct and efficient, especially when dealing with external moisture. It also has the added benefit of replenishing the transformer's insulating oil.

Limitations: This approach may not be as effective for deeply ingrained moisture, especially within thick layers of paper insulation. Vacuum Drying:

Principle: This method uses a vacuum to reduce the boiling point of water, allowing it to evaporate at lower temperatures.

Procedure: The transformer is subjected to a vacuum, and any moisture present in the insulation system starts evaporating. The evaporated moisture is then drawn out using vacuum pumps.?

Advantages: Can achieve very low moisture levels, relatively fast, and suitable for large transformers.

Limitations: The process can be slow if the moisture content is very high initially, potential risk for older transformers if not done correctly.

The process of vacuuming a transformer using a BV vacuum unit

Oven Drying:

Principle: Using heat to drive out moisture.

Procedure: Smaller transformers or transformer components are placed in a large oven where they are subjected to controlled heat to evaporate the moisture. The moisture-laden air is then vented out.

Advantages: Simple and straightforward, effective for smaller units.

Limitations: Not suitable for large transformers, energy-intensive.

But what if the paper insulation is saturated to a bigger degree? Or sources are limited? Simply attempting to dry the paper by targeting the oil is akin to chasing shadows. It's in such scenarios that techniques like a transformer drying process with low frequency heating shows its effectiveness.

Transformer vacuum Oven US

Transformer drying process with low frequency heating?

Although the traditional methods serve their purpose, the low-frequency drying approach emerges as an alternative. The LFD (Low Frequency Dryer) device by GlobeCore operates on a principle that leverages low-frequency electric currents. These currents flow through the transformer windings, elevating their temperature to a standard drying range of +75°C to +120°C. The uniqueness of this method stems from its heating dynamics. As the low-frequency currents heat, the source of warmth becomes the winding itself. This means the heat generation starts internally. Consequently, moisture evacuation from the insulation's depth is not only faster but also more comprehensive when pitted against other heating techniques.

Main Idea of Low Frequency Heating Method

To optimize the efficiency of drying oil-filled transformers, the LFD (Low Frequency Dryer) device is often paired with CMM thermal vacuum dryers. This combined approach offers a dual advantage. Firstly, it facilitates direct heating of the transformer's windings. Simultaneously, it ensures the moisture—released from the windings into the oil—is efficiently extracted. This two-pronged process guarantees a thorough drying experience.

The process of connecting the low-frequency heating device LFD (Low Frequency Dryer) to the transformer

For situations where the oil has been drained from the transformer, leveraging the LFD (Low Frequency Dryer) device in tandem with BV or UVV or Mojave Heat units proves highly effective. These units are adept at addressing moisture that has migrated from the windings to the transformer tank.

In a realm where operational efficiency, longevity, and safety are paramount, embracing such modern techniques is not just preferable but essential. As the energy landscape continues to evolve and demands on transformers intensify, it is imperative that the industry rethinks its strategies, turning to methods that promise not just short-term relief but long-term resilience. The future of transformer maintenance, it seems, is not just about adapting to new challenges, but preemptively addressing them with the best tools at our disposal.

Jane Doroshenko

Business Development Manager

[email protected]

+4942136583207