What happens to the bus voltage when a long transmission line is connected from that bus and the other end is left open?

What happens to the bus voltage when a long transmission line is connected from that bus and the other end is left open?

• A. Bus voltage will decrease
• B. MVARs would begin flowing into the open-ended line
• C. Nothing
• D. Bus voltage would increase

Answer: (D)

When a long transmission line is connected to a bus and the far end is left open, the bus voltage is expected to increase. This phenomenon occurs due to the characteristics of long transmission lines, which can be modeled using parameters such as resistance, inductance, capacitance, and admittance. As the line is energized but is not connected to any load at the open end, the capacitance of the line becomes significant. In this scenario, the line can generate reactive power (measured in MVARs), causing an increase in the voltage at the sending end, which is the bus in this case. The line essentially acts as a capacitor, leading to a rise in voltage because the reactive power supplied causes a voltage rise at the bus connected to it. This behavior is particularly notable in long lines where the capacitive effect is more pronounced because the line can produce a considerable amount of capacitive reactive power, significantly affecting the overall voltage at the bus. Thus, when the transmission line is left open, the bus voltage will indeed increase due to these capacitive effects.

When a long transmission line is connected to a bus and the far end is left open, the bus voltage is expected to increase. This phenomenon occurs due to the characteristics of long transmission lines, which can be modeled using parameters such as resistance, inductance, capacitance, and admittance.

As the line is energized but is not connected to any load at the open end, the capacitance of the line becomes significant. In this scenario, the line can generate reactive power (measured in MVARs), causing an increase in the voltage at the sending end, which is the bus in this case. The line essentially acts as a capacitor, leading to a rise in voltage because the reactive power supplied causes a voltage rise at the bus connected to it.

This behavior is particularly notable in long lines where the capacitive effect is more pronounced because the line can produce a considerable amount of capacitive reactive power, significantly affecting the overall voltage at the bus. Thus, when the transmission line is left open, the bus voltage will indeed increase due to these capacitive effects.