Solving Chemical Compatibility Concerns When Adding a New Adhesive Tape to an Oil Filled Transformer System
The power grid connects power plants, transmission lines and distribution centers to supply electrical power to end users. Being a critical part of the power grid system, transformers are responsible for converting voltage levels either up or down to transmit electricity to consumers, making the longevity of these systems imperative to our everyday life.
The life of a transformer is expected to be > 25 years and the integrity of the insulation system in the transformer is essential to guarantee long-term performance. Since oil is more efficient at cooling, the majority of power and distribution transformers are liquid type (oil cooled) versus dry type (air cooled), allowing for a smaller footprint and higher power ratings. The materials used within the insulation system play a critical role in achieving a longer lifespan for each transformer.
Where are adhesive tapes used in oil filled transformers?
Adhesive tapes are used throughout the coil windings to secure other solid insulation materials such as the paper layer insulation. Most commonly, the adhesive tapes used in these applications involve high tensile strength, glass filament reinforced polyester or paper backed tapes with acrylic adhesive. The porosity of a paper backed tape is particularly beneficial for the absorption of oil which enhances overall dielectric performance by minimizing unwanted air voids in the transformer winding.
How the addition of new material can impact transformer performance
Oil filled transformer OEMs will commonly measure insulation performance characteristics on the oil when adding a new material to their design, such as a new adhesive tape. Once the transformers are in operation, users will periodically test the oil to understand the health of their equipment and oil aging trends over time. As oil ages and oxidizes, a sludge can form resulting in decreased circulation of the cooling oil which leads to decreased performance of the transformer and potential failure. Oil can also become contaminated by the aging of the other solid insulation materials including the adhesive tape.
Top Considerations When Evaluating an Adhesive Tape in Oil
Validating the chemical compatibility of an adhesive tape in transformer oil involves the following:
- The type of oil(s) used is an important consideration. For example, some mineral oils can be more “harsh” than others in terms of oxidation potential. The higher the aromatic content of the oil, the more likely it will chemically interact with another component, such as the adhesive tape, and result in degraded performance.
- The adhesive formulation of the tape is another consideration. Common pressure sensitive adhesives include rubber, acrylic or silicone. The ideal choice for oil compatibility and superior adhesion is an acrylic adhesive. There are many variations in acrylic adhesive formulations which is an important factor for chemical compatibility.
Key tests to evaluate compatibility of an adhesive tape in oil
The compatibility of an adhesive tape in oil can be verified based on a few key tests on thermally aged oil that has been exposed to the adhesive tape.
Examples of oil monitoring tests include:
- Interfacial Tension
- Acidity
- Dielectric Strength
- Oil Color
All of these tests monitor the “health” of the oil and can indicate if there is contamination from other products such as the tape.
Supplemental tests to consider include:
- Peel adhesion of the tape before and after oil exposure
- Visual inspection of the tape before and after oil exposure
Saint-Gobain® Oil Compatible Tapes
Saint-Gobain Tape Solutions adhesive tapes have been tested in a variety of transformer oils and our experts understand the adhesive chemistry interactions with oil. We have a wide selection of high-performance electrical insulation tapes with proven compatibility in transformer oils by many OEMs. A few examples include our glass filament reinforced PET tapes such as PS.25, PS.30 and PS.249, as well as reinforced paper based tape 6601. All of these tapes are formulated with acrylic adhesives, which is known for chemical stability, superior adhesion and long-term thermal capabilities.
Trust Saint-Gobain Tape Solutions to help you determine the best tape to use in your transformer oil to ensure chemical compatibility and long-term reliability. In instances where a solution is not available for a given application, our tape development engineers are ready to formulate a custom tape solution to address your needs.
For more information on our broad portfolio of high-performance electrical insulation tapes view our Tape Solutions for Electrical Insulation or contact us today.
