Correct option is A
Voltage instability in power systems is primarily related to the inability of the system to maintain acceptable voltage levels when subjected to disturbances or changes in load. This instability is often a result of insufficient reactive power support, which is essential for maintaining voltage levels throughout the network.
Explanation:
1. Reactive Power and Voltage Stability:
o Reactive power (measured in VARs) is crucial for maintaining voltage levels in a power system. It helps in regulating voltage by providing the necessary voltage support at different points in the network.
o Voltage instability occurs when the power system cannot provide adequate reactive power to maintain voltage levels, leading to voltage collapse or large voltage fluctuations.
2. Active Power and Voltage Stability:
o While active power (measured in watts) is important for energy transfer and load demand, it does not directly affect voltage stability in the same way reactive power does. Voltage stability issues are more associated with the reactive power component.
3. DC Power and Harmonic Power:
o DC power and harmonic power are not typically involved in the context of voltage stability in AC power systems. DC power transfer is related to specific applications like HVDC transmission, and harmonic power refers to distortion components that affect power quality but are not the main cause of voltage instability.
Therefore, the factor that mainly leads to voltage instability is the transfer of reactive power. When the system cannot provide or absorb sufficient reactive power, voltage instability can occur.
