What is the primary purpose of using a transformer in power transmission?

The primary purpose of using a transformer in power transmission is to modify voltage levels so that electricity can be transmitted efficiently over long distances. When a transformer is used to increase the voltage at the sending end, it allows for power to be transmitted with lower current, which in turn minimizes resistive losses in the wires. This process also reduces the electrical and thermal stress on transmission lines and other components.

While the statement about reducing corona loss at towers may have some relevance in specific contexts, it does not capture the fundamental purpose of transformers in power transmission. Transformers are essential for adjusting voltage levels to suitable values for efficient transmission, while the other options suggest functions that are not primarily what transformers are designed to do. For instance, decreasing wire size, while it may seem beneficial, is not directly a function of a transformer but rather a consideration related to material engineering and design. Changing frequency is typically handled by different equipment like converters rather than transformers. Thus, the focus of a transformer is fundamentally on voltage adjustment to optimize power transmission efficiency.