Transformer Oil Purifiers and Their Supporting Equipment in Power Systems

Transformer oil, both as an insulator and a coolant, is critical in the reliable and safe operation of transformers in power systems. Nevertheless, the quality of transformer oil degrades over time as a result of several factors that result in the presence of harmful constituents such as moisture, impurities, and acidic materials. These contaminants affect the thermal stability as well as the insulating characteristics of the oil, which may lead to transformer flashovers as well as explosions. Transformer oil purifiers bridge this gap by employing physical methods to assist in maintaining oil quality and ensuring optimum transformer performance. This article discusses the basic operations of transformer oil purifiers, reviews the necessary ancillary equipment they typically interface with, and discusses major considerations in using them successfully in power systems.

What are the Working Principles of Transformer Oil Purifiers?

To counter the constant aging of transformer oil and keep the fluid at peak performance, purpose-built purifiers rely on mechanisms engineered to fend off the main deteriorative effects. Coordinated physical approaches strip unwanted agents such as water, particulate matter, and reactive acidic species. The purification principles can be summarized as follows:

• Vacuum Dehydration: A controlled, low-pressure zone is set up inside the unit. Under this condition, water dissolved in the oil boils at a much lower temperature, making it easy to vaporize and overload the vapor phase along with the circulating oil, thus dragging the moisture away.
• Filtration: The oil flows through stacked filter stages, progressively finer in mesh. Each stage picks up finer particulates—grime, metal wear, and by-products of oil breakdown—yet transparent, keeping the ensuing oil stream inside the transformer low in particulate contaminants.
• Adsorption: Inside the vessel, powdered activated clay or similar absorbing agents partition the flow. These fillers present a broad surface, and their micro-structured pores offer a jumping surface onto which the acid ethers, constantly rising in concentration through transformer activity, preferentially latch. These complexes may then be dumped or baked off during periodic boiler regeneration, refreshing the tower section.

What are the Functions of Transformer Oil Purifiers?

Through these cleaning processes, transformer oil purifiers render several critical benefits:

• Elimination of Water: Water is the most significant cause of electrical malfunction in transformer oil. Through efficient elimination of dissolved as well as free water, purifiers significantly reduce the possibility of transformer failure.
• Elimination of Particulates: Solid contaminants may impede oil flow as well as reduce its insulation property. Purifiers ensure cleaner oil through elimination of such ruinous particulates.
• Acid Neutralization: Transformer oil is decomposed by acidic waste materials and can lead to corrosion of internal components. Purifiers take out these acidic materials, thus extending the transformer oil’s life.
• Higher Dielectric Breakdown Voltage (BDV): BDV tests an oil’s strength against electrical stress. Purified oil contains a higher BDV, which gives higher insulation and lower electrical breakdown probability.
• Increased Oil Flow: By removing contaminants that cause oil flow interruptions, purifiers provide unobstructed flow in the transformer, leading to increased heat dissipation and effective cooling.

Supporting Equipment for Transformer Oil Purifiers

Along with transformer oil purifiers, some equipment is employed to serve supporting functions in maximizing the purification process and keeping maximum quality of oil. Some supporting equipment that is typically employed includes:

1. Vacuum Pumping Unit

The vacuum pumping unit is the central component of the vacuum dehydration process. It significantly reduces the pressure within the chamber of the purifier. The decrease in pressure has a direct effect on the boiling point of the transformer oil, decreasing it. With the reduced boiling point, the moisture trapped by the oil escapes freely, which makes it possible to drain the oil with ease.
There are several types of vacuum pumps that exist, each having different operational characteristics and applications. Let’s take a closer look at two of the most common types:

• Rotary Vane Pumps: Rotary vane pumps are most suitable for delivering high pumping speeds, particularly at low vacuum levels. They are most suited in cases where quick initial dehydration is needed.
• Roots Blowers: If a higher vacuum is strictly necessary, roots blowers prove to be the most appropriate choice. They are most effective during the second half of the dehydration process, when removing the most stubborn of moisture molecules requires a more powerful vacuum environment.

2. Dry Air Generator

Sometimes, transformer oil may require a further process to achieve very low moisture levels. This is where dry air generators come in. These generators produce virtually moisture-free air. This dry air is then applied in a purging process. During purging, dry air is passed through the oil, further stripping out any residual moisture that might still be present after the initial vacuum dehydration process. This second process is particularly helpful when dealing with very degraded oil or when the highest possible level of moisture removal is wanted.

3. Transformer Oil BDV Tester

The transformer oil BDV tester is the most important equipment to determine the insulating characteristics of the oil. It measures the specific voltage level at which the oil is not able to perform as an insulator, and electrical breakdown occurs. This valuable reading is known as the breakdown voltage (BDV). Having a high BDV indicates that the oil will be capable of withstanding high voltage stresses within the transformer without compromising its insulating characteristics. Transformer oil purifiers attempt to raise the BDV of the oil quite significantly by removing impurities that have the effect of lowering its insulating strength. BDV values before and after purification, the effectiveness of the treatment can be directly assessed.

4. Oil Analysis Equipment

To achieve the best oil purification results, it’s essential to analyze the characteristics of the oil in advance and after processing. It’s performed on specialized equipment for oil analysis. These devices tend to find the most applicable parameters, telling us much about the condition of the oil, e.g.,

• Moisture Content: This measurement directly reads the amount of water that is present in the oil. A before-and-after purification comparison permits measuring the effectiveness of moisture elimination.
• Acid Value: It is a value that indicates that there are acidic degradation products in the oil. Acids are harmful to the insulating quality of the oil and cause further degradation. The reduction of acid value achieved through the purification process is aided by the equipment utilized for oil analysis.
• Interfacial Tension: This characteristic indicates the cohesive forces between oil molecules. Good interfacial tension is the indicator of a healthy oil, and it plays a key role in the lubricating and insulating properties of the oil. Examination of this parameter enables us to check whether purification has restored the best interfacial tension of the oil.

Through examination of these major parameters, oil analysis equipment yields essential information to assess the efficacy of the transformer oil purification process.

5. Control System

Modern transformer oil purifiers often incorporate a sophisticated control system. This system automates the entire purification process, ensuring consistent and reliable operation. The control system precisely regulates factors like temperature, pressure, and flow rates to optimize the purification process for the specific oil being treated. Additionally, the control system can be integrated with other automated equipment or monitoring systems within the power grid. This allows for remote control and data acquisition of the purification process, enabling operators to monitor progress and make adjustments as needed.

6. Waste Oil Handling Equipment

After purification, some of the transformer oil can be determined to be unfit for reuse in the transformer due to excess degradation. This “waste oil” needs to be specially handled and disposed of to minimize environmental hazards. Special waste oil handling equipment comes into the picture here.

• Oil Filtration Systems for Waste Oil: Based on the level of contamination, in certain instances, waste oil can undergo additional treatment by specialized filtration systems. They may employ filter elements with a smaller pore size to remove residual impurities that could not be addressed by the primary transformer oil purifier. This process may not always be feasible for severely degraded oil.
• Waste Oil Dehydration Systems: Similar to dehydration in the main purifier, independent dehydration systems can be used for waste oil. These can be designed for the removal of high water content found in very contaminated oil before final disposal.
• Oil Recycling Plants: Preferably, wherever possible, used oil is to be recycled by specialized plants. These plants employ advanced processing techniques to recover usable oil components, minimizing wastage and maximizing environmental sustainability.

Considerations for Effective Transformer Oil Purification

For maximum efficiency in transformer oil purification and the optimum condition of the transformers, several important factors are involved:

1. Transformer Oil Purifier Selection: The appropriate capacity and size of the purifier should be chosen. All the following parameters influence this selection: transformer oil volume, flow rate required, and degree of contamination.
2. Pre-filtration: A pre-filtration process might be advantageous before the main purification process, particularly for very dirty oil. Pre-filtration removes large particles, which protects the major filtration media and enhances overall treatment efficiency.
3. Oil Sampling and Analysis: Ongoing oil sampling and analysis are essential practices. Monitoring oil quality trends regularly enables maintenance plans to be launched proactively, planning oil purification before oil degradation sets in.
4. Operational Procedures: Abiding by established operational procedures in the purification of transformer oil is necessary. They specify safe handling procedures, proper equipment setup, and optimal process conditions for effective oil treatment.
5. Environmental Regulations: Proper compliance with environmental regulations in the disposal of waste oil is necessary. This helps ensure proper waste oil management as well as minimizing environmental impacts.

Conclusion

Transformer oil purifiers form a core component of preventative maintenance procedures in power grids. By eliminating contaminants and recovering the insulation characteristics of transformer oil, they help transformers run both reliably and safely. Ancillary equipment such as vacuum pump sets, dry air plants, and transformer oil BDV testers complements the purification process. Proper management of waste oil through filtration systems, dehydration systems, and cooperation with properly licensed waste disposal contractors is equally important to preserving environmental health. Through the use of such practices, power system operators can achieve maximum transformer oil management to provide for long-term transformer health and reliability.