PJM Transmission Practice Test

In the context of power transmission, a high-voltage line such as a 500kV line that is loaded at 250 MW primarily behaves like a capacitor when considering its reactive power characteristics. This phenomenon occurs due to the effects of line capacitance and how it interacts with the inductive loads.

When a transmission line operates, it not only transmits active power but also reactive power. The capacitive nature of the line becomes prominent, especially under certain loading conditions. If the load creates a lagging power factor (common with inductive loads), the line's inherent capacitance can help neutralize some of that inductance by providing leading reactive power. As a result, at certain load levels and configurations, particularly long transmission lines, the overall effect can be capacitive.

Furthermore, high-voltage lines have significant capacitance which can allow them to behave like a capacitor relative to the load. The capacitance can alleviate voltage drops along the line and contribute to voltage support at the receiving end. Thus, identifying the primary reactive power behavior of the line helps in analyzing system stability and performance in transmission scenarios.

The other options refer to entirely different roles in power systems: inductors handle energy storage in magnetic fields, transformers adjust voltage levels while maintaining power