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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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In series line compensation, the voltage stability is
Stable
Improves
Deteriorates
Unstable
Improves
Quick Summary: Series line compensation involves adding a capacitor in series with the transmission line to reduce the overall inductive reactance of the system. By reducing the line impedance ($X_{eq} = X_L - X_C$), the power transfer capability is enhanced, and the voltage regulation is improved.
Series line compensation involves adding a capacitor in series with the transmission line to reduce the overall inductive reactance of the system. By reducing the line impedance (Xeq=XL−XC), the power transfer capability is enhanced, and the voltage regulation is improved.
P=XL−XCVsVrsinδ — Power transfer capability increases as XC reduces net reactance
Vdrop≈I(Rcosϕ+(XL−XC)sinϕ) — Voltage drop expression showing reduction with series compensation
The transmission line voltage drop is proportional to the reactive component of the impedance. By inserting a series capacitor, the total line reactance is neutralized, which decreases the voltage drop across the line for a given power flow. This leads to better voltage regulation and increased stability margins by pushing the power-angle curve higher, allowing more stable power transfer for the same angular displacement.
Series compensation is used primarily in long-distance EHV transmission lines.
It directly reduces the inductive voltage drop by compensating for line inductance.
It increases the steady-state power transfer limit of the transmission system.
Potential risk includes sub-synchronous resonance (SSR) if not properly controlled.
Increased power transmission capacity
Improved transient and steady-state stability
Better voltage profile regulation
Effective control of load sharing between parallel lines
Risk of sub-synchronous resonance (SSR)
Requires high-voltage insulation and protection for capacitor banks
Need for complex fast-acting protective bypass switches
Long EHV and UHV transmission lines
Interconnection between large grids
Lines where power flow control is required dynamically
Series compensation is generally preferred for long lines (>300 km) to improve voltage regulation without the need for additional generating stations.
Option D is incorrect because compensation is a stability enhancement measure, not a cause of instability.
B is correct — Series line compensation reduces the total line reactance, which minimizes voltage drops and increases the maximum stable power transfer capacity of the system.
Always remember that while series compensation improves stability, shunt compensation is primarily used for voltage regulation at load ends. Distinguishing between these two is critical for exam questions.