What device is used to automatically adjust the primary voltage of a line?

The device used to automatically adjust the primary voltage of a line is a regulator. Voltage regulators play a crucial role in maintaining a consistent voltage level across the electrical distribution system. They automatically sense variations in voltage due to changes in load or other factors and make necessary adjustments to ensure that the voltage remains within predefined limits.

This is especially important in maintaining the reliability of the electrical supply and protecting equipment from voltage fluctuations that could potentially cause damage. Regulators can be equipped with different control mechanisms to ensure they respond appropriately to changes in the system, making them essential for stabilizing voltage levels over long distances and across varying load conditions.

Transformers, while important for stepping voltage levels up or down, do not actively adjust voltage but rather change it based on their configuration. Switchgear is typically involved in the protection and switching of electrical circuits rather than voltage regulation. Capacitors, on the other hand, are used for power factor correction and reactive power support but do not autonomously regulate voltage levels. Thus, the function of a regulator distinctly aligns with the task of automatically adjusting primary voltage in an electrical line.