Stability of a power system can be improved by1.Using series compensations2.Using parallel transmission lines3.Reducing voltage of transmissionWhich of the above statements are correct?

Correct Answer: D - 1 and 2 only

Quick Concept Explanation

Power-system stability concerns the ability of synchronous machines and network states to remain or return to acceptable operation after disturbances. Series compensation can increase transfer capability by reducing effective reactance, and parallel transmission paths can reduce transfer reactance. Key relation: Simplified transfer P≈(EV/X)sinδ; reducing effective X raises transfer capability.

Exam focus: Lower transfer reactance generally improves synchronizing power margin. Common trap: Do not confuse ordinary load flow with a dynamic stability study.

Statement-wise Verification

• Statement 1 - Correct.
  Using series compensations
  Series compensation can increase transfer capability by reducing effective reactance, and parallel transmission paths can reduce transfer reactance.
• Statement 2 - Correct.
  Using parallel transmission lines
  Series compensation can increase transfer capability by reducing effective reactance, and parallel transmission paths can reduce transfer reactance.
• Statement 3 - Incorrect.
  Reducing voltage of transmission
  Lower transmission voltage generally worsens power-transfer capability/stability; higher voltage helps

Core Concept

Power-system stability concerns the ability of synchronous machines and network states to remain or return to acceptable operation after disturbances. Series compensation can increase transfer capability by reducing effective reactance, and parallel transmission paths can reduce transfer reactance. Stability studies focus strongly on rotor-angle/electromechanical dynamics rather than ordinary steady-state voltage calculation alone.

Formula / Key Relationship

Simplified transfer P≈(EV/X)sinδ; reducing effective X raises transfer capability.

Why the Other Options Are Wrong

Option A is incorrect because it omits correct statement(s) 2. Option B is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 1. Option C is incorrect because it omits correct statement(s) 1.

Exam Shortcut / Approach

Lower transfer reactance generally improves synchronizing power margin.

Common Mistake

Do not confuse ordinary load flow with a dynamic stability study.

Quick Revision

Series Compensation and Parallel Lines is linked with Stability Improvement, Power System Stability and Power Systems. Lower transfer reactance generally improves synchronizing power margin.