Question

Which of the following mainly leads to voltage instability?
1. Transfer of reactive power
2. Transfer of active power
3. Transfer of dc power
4. Transfer of harmonic power

Answer 1

Correct Answer - Option 1 : Transfer of reactive power

Voltage instability:

• Voltage instability may result in the form of a progressive fall or rise of voltage of some load buses. The possible outcome of voltage instability is loss of load in the area where voltages reach unacceptably low values, or a loss of integrity of the power system.
• The main factor contributing to voltage instability is usually the voltage drop that occurs when reactive power flow through inductive reactance associated with the transmission network; this limits the capability of transmission network for power transfer.
• The power transfer limit is further limited when some of the generators hit their reactive power capability limits.
• The driving force for voltage instability is the loads; in response to a disturbance, power consumed by the loads tends to be restored by the action of distribution voltage regulators, tap changing transformers, and thermostats.