Steady-state stability of a power system is improved by

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Examoogle · Accepted Answer

Using double circuit line instead of single circuit line

Explanation: Steady-state stability of a power system is defined by its ability to maintain synchronism under small disturbances. It is directly proportional to the synchronizing power coefficient, which increases when the total reactance of the transmission system is reduced.

Working Principle: The maximum power transfer in a transmission line is given by $P_{max} = \frac{V_s V_r}{X}$. By using a double circuit line instead of a single circuit line, the equivalent reactance $X$ of the path between the sending and receiving ends is halved (assuming parallel lines of identical parameters). This reduction in total reactance significantly increases the maximum power transfer capability and the steady-state stability limit.

Key Formulas: $P = \frac{V_s V_r}{X} \sin(\delta)$ — Power transfer equation; $X_{eq} = \frac{X_{line}}{n}$ — Equivalent reactance for $n$ parallel circuits

Key Points: Steady-state stability depends on maintaining small angular displacement $\delta$.; Reducing line reactance is the most effective passive method to improve stability.; Double circuit lines reduce the net impedance seen by the generator.

Advantages: Increases the maximum power transfer limit; Reduces transmission line voltage drop; Improves system reliability during single line outages

Disadvantages: Higher initial capital expenditure; Increased right-of-way requirements

Applications: Long-distance power transmission lines; Interconnected grid networks

Additional Info: Fault clearing time (Option A) relates to transient stability, not steady-state.. Increasing generator inertia (the opposite of Option D) helps improve stability.. Single pole switching (Option C) is a transient stability improvement measure.

Answer: B is correct — Using double circuit lines decreases the total transmission line reactance, thereby increasing the maximum synchronizing power limit.

Exam Tip: Always differentiate between steady-state stability (improving reactance/voltage profile) and transient stability (faster fault clearing/quick excitation systems).

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