In shunt line compensation, the magnitude of critical receiving end voltage and critical power angle is
A
Stable
B
Deteriorates
C
Improve
D
Unstable

Question

In shunt line compensation, the magnitude of critical receiving end voltage and critical power angle is

Examoogle · Accepted Answer

Improve

Explanation: Shunt line compensation involves adding reactive power elements like shunt capacitors or reactors to a transmission line. This configuration improves the voltage profile and increases the stability limit by modifying the receiving end voltage magnitude and reducing the power angle $\delta$ required to transmit a specific amount of power.

Working Principle: Shunt capacitors compensate for inductive reactance and inject reactive power ($Q = V^2 B$), which boosts the receiving end voltage ($V_R$). By increasing $V_R$, the power transfer capability ($P = \frac{V_S V_R}{X} \sin \delta$) is enhanced, which allows the line to maintain the same power flow at a smaller power angle $\delta$, thereby improving both voltage stability and steady-state stability.

Key Formulas: $P = \frac{|V_S| |V_R|}{X} \sin \delta$ — Power transfer equation; $Q_{shunt} = V^2 \cdot B$ — Reactive power compensation

Key Points: Shunt compensation is primarily used for voltage regulation.; It helps in maintaining the voltage profile along the transmission line.; The power angle $\delta$ is the phase difference between sending and receiving end voltages.; Smaller power angle $\delta$ implies higher transient and steady-state stability.

Advantages: Improved voltage regulation; Increased steady-state stability limit; Reduced transmission losses during light load conditions

Disadvantages: May cause overvoltage during low load conditions if not switched; Additional capital cost for reactive power equipment

Applications: Long EHV/UHV transmission lines; Weak power systems with heavy load fluctuations

Additional Info: The critical power angle is the maximum angular displacement before the system loses synchronism.. Option D (Unstable) is incorrect because compensation is specifically designed to stabilize the system.. Options A and B represent states of the system rather than the improvement effect sought by the installation of shunt devices.

Answer: C is correct — Shunt line compensation improves the magnitude of receiving end voltage and reduces the power angle to enhance system stability.

Exam Tip: Always remember that shunt compensation fixes voltage at specific nodes, whereas series compensation is used to reduce the effective line impedance $X$ to increase the power transfer limit.

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