Which Type of Oil is Used in Current Transformers?

Current transformers (CTs) play a vital role in electrical systems by converting high currents into lower, more manageable values. One crucial aspect of CTs is the type of oil used in the transformers, which ensures both insulation and cooling. This article will explore the different types of transformer oils, their significance, and the applications in CTs.

The Role of Transformer Oil in CTs

Transformer oil serves a dual purpose in CTs: it insulates the windings and other components, and it also cools the transformer by absorbing and dissipating heat. This oil is primarily categorized into two types: mineral oil and synthetic oil. Mineral oil is the most commonly used type, but it is important to understand both forms and their applications in CTs.

Mineral Oil: A Stable Choice for Transformer Insulation

Mineral oil is a pure form of transformer oil that is free from fatty acids, making it highly stable at high temperatures. It is derived from crude oil and is known for its excellent insulating properties. Mineral oil is the primary choice for many transformer applications due to its cost-effectiveness and reliability. It is used in both naphthenic and paraffinic based oils, each with its own unique characteristics.

Types of Mineral Oil Based on Structure

Naphthenic Oil: Naphthenic oil is known for its excellent thermal stability, which makes it ideal for applications where high temperatures are encountered. It is commonly used in oil-cooled transformers, including CTs. Naphthenic oil has a high pour point and a low viscosity, which helps in efficient heat dissipation. Paraffinic Oil: Paraffinic oil, on the other hand, is characterized by its low pour point and high viscosity. It is typically used in a broader range of applications, including some CT models where space and design constraints are significant. Paraffinic oil is also stable at high temperatures and is less likely to degrade over time.

Cooling Techniques in Current Transformers

The choice of cooling technique for CTs is determined by the application and the voltage class of the transformer. Most CTs are air-cooled, but for higher voltage classes, alternative cooling methods are necessary. Oil-cooled transformers, including CTs, are designed to withstand higher electrical loads and require oil for both insulation and cooling. Paraffin/naphtha-based oils are commonly used in these transformers due to their specific properties that make them suitable for such applications.

Alternative Cooling Methods in CTs

Resin-Cooled Cast Resin-Epoxy Transformers: These transformers use resin as the cooling medium, which encapsulates the windings. This method is commonly used in low-to-medium voltage applications. The resin provides excellent protection against physical damage and can handle varying environmental conditions. Air-Cooled Transformers: Air-cooled transformers are the most common type, where heat is dissipated directly from the windings to the surrounding air. This method is simple and cost-effective but may not be suitable for high-power transformers.

Conclusion

Transformer oil is an essential component in current transformers, serving as both an insulator and a coolant. While mineral oil is the most commonly used type, synthetic oil has also gained popularity for specific applications. The choice of oil and cooling method depends on the application and the design requirements of the transformer. Understanding these aspects ensures optimal performance and longevity of the transformer in various electrical systems.

Related Keywords

Current Transformers Transformer Oil Mineral Oil Naphthenic Oil Paraffinic Oil