What happens if the system voltage remains below .9 p.u. for an extended period?

• A. Automatic generation control activates
• B. Manual load reduction may be required
• C. No actions are necessary
• D. Firm load disconnection is mandatory

Answer: (B)

When system voltage remains below 0.9 per unit (p.u.) for an extended period, it can lead to voltage instability and affect the overall reliability of the power system. Under these conditions, manual load reduction may be required as a corrective action to prevent further degradation of the system and to restore voltage levels to acceptable ranges. Load reduction helps balance the supply and demand, reducing the strain on the system, and can aid in the recovery of voltage levels.

Each power system has specific thresholds for acceptable voltage levels. Operating below 0.9 p.u. indicates a significant voltage drop that could result in equipment damage or failure in maintaining service. Therefore, proactive measures such as load reduction become necessary to ensure system stability and the safety of both the infrastructure and consumers.

Other actions might include the potential for automatic generation control or monitoring for possible disconnections, but typically, initial corrective measures will focus on manual interventions like load shedding rather than immediate disconnections or relying solely on automatic systems.