Understanding Transformer Fundamentals: Types and Applications

Transformers play a crucial role in the electrical power industry, particularly when it comes to the generation and distribution of electricity. Various types of transformers serve specific functions, and knowing their fundamentals can provide insights into how they operate within generating stations and other facilities. This article explores the key aspects of several transformer types, including tap-changing mechanisms, unit auxiliaries, and interconnecting transformers.

One common type is the generator transformer, which often features a tap-changing mechanism designed for minor variations in high voltage (HV) levels, typically around 5%. These transformers are essential for controlling voltage through field excitation. Some generator transformers may utilize an on-load tap-changing mechanism for reactive power control, which is useful in maintaining system stability. Efficient cooling solutions, such as compact unit-coolers and oil-to-water heat exchangers, are often incorporated to manage space constraints within generating stations.

Unit auxiliary transformers serve another important purpose, primarily stepping down voltage from the generator output to supply power to auxiliary equipment within the station. With a secondary voltage around 6.9 kV, these transformers ensure that essential systems run smoothly during generation. Meanwhile, station transformers are crucial during both setup and operational phases, providing power to auxiliary equipment as the generators are started up.

Interconnecting transformers and autotransformers facilitate connections between systems operating at different voltage levels. These transformers do not provide electrical isolation between primary and secondary windings, which can result in cost-effective designs. Their wide tapping range and delta-connected tertiary windings help stabilize the system, and provisions for reactive power compensation can be made through synchronous condensers or shunt reactors.

Lastly, receiving station transformers are designed to step down transmission voltages to levels suitable for primary feeders, such as 220 kV/33 kV configurations. These transformers are particularly important for feeding industrial plants and must contend with variable load conditions. Automatic tap changing on load is essential for managing voltage variations, and noise considerations are crucial when transformers are located near residential areas.

By understanding these transformer fundamentals, one can appreciate the complexity and functionality of electrical systems that power our daily lives. Each transformer type has its unique characteristics and applications, ensuring that electrical energy is transmitted efficiently and reliably.