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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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The transient stability limit of a power system can be appreciably increased by introducing
Series inductance
Shunt inductance
Series capacitance
Shunt capacitance
Series capacitance
Quick Summary: The transient stability limit of a transmission line is increased by introducing series capacitance because it compensates for the inherent line inductive reactance. By reducing the overall transfer reactance between the sending and receiving ends, the power-angle characteristic is improved, allowing higher power transfer for a given angular stability margin.
The transient stability limit of a transmission line is increased by introducing series capacitance because it compensates for the inherent line inductive reactance. By reducing the overall transfer reactance between the sending and receiving ends, the power-angle characteristic is improved, allowing higher power transfer for a given angular stability margin.
P=XL−XCVsVrsin(δ) — Power transfer equation with series compensation
Xeq=XL−XC — Effective reactance of the compensated line
The steady-state power transfer capability of a line is defined by P=XeqVsVrsin(δ). By placing a capacitor in series with the line, the equivalent reactance Xeq=XL−XC decreases. This reduction in series reactance directly increases the maximum power transfer limit (Pmax=XeqVsVr) and allows the system to remain stable under transient disturbances by providing a stiffer coupling between the generator and the infinite bus.
Series compensation reduces the effective line reactance (XL−XC).
It enhances the steady-state and transient stability limits of the power system.
Improves voltage regulation and load division among parallel lines.
Potential risk of sub-synchronous resonance (SSR) must be managed.
Increased power transfer capability
Improved transient stability
Better voltage profile control along long lines
Risk of sub-synchronous resonance (SSR)
Requires complex protection schemes (e.g., fast bypass gap protection)
Higher installation and maintenance costs
Long-distance EHV and UHV transmission lines
Inter-area power corridors to increase capacity
Series compensation is expressed as a percentage of line reactance, typically 30% to 70%.
Shunt inductance is used for Ferranti effect control (light load conditions), whereas series capacitance is for power transfer enhancement.
Shunt capacitance is used for local reactive power support (voltage improvement) but does not directly decrease series line reactance.
C is correct — Introducing series capacitance reduces the line's effective inductive reactance, thereby increasing the power-angle stability limit.
Always remember: Series elements modify the line's electrical length (reactance), while shunt elements modify the voltage profile at the buses.