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Examoogle • User • info@examoogle.com • EE-2024-8821
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In series line compensation, the degree of compensation is usually in the range of
to 0.8
to 0.6
to 0.5
to 0.25
to 0.8
Quick Summary: In series line compensation, the degree of compensation (k) is defined as the ratio of the reactance of the series capacitor ($X_c$) to the total line reactance ($X_L$). The typical range for practical power system stability improvement is 30% to 80% (0.3 to 0.8), as values beyond this can trigger subsynchronous resonance (SSR) issues.
In series line compensation, the degree of compensation (k) is defined as the ratio of the reactance of the series capacitor (Xc) to the total line reactance (XL). The typical range for practical power system stability improvement is 30% to 80% (0.3 to 0.8), as values beyond this can trigger subsynchronous resonance (SSR) issues.
k=XLXc — Definition of degree of compensation
Pmax=XL(1−k)V2 — Impact of compensation on maximum power transfer
The series capacitor compensates for the inductive reactance of the transmission line, effectively shortening the electrical length of the line. By reducing the net series reactance (Xnet=XL−Xc), the power transfer capability is significantly increased according to the power-angle equation P=XL−XcV1V2sin(δ).
Series compensation is used to increase the steady-state power transfer capacity.
It reduces the effective voltage drop across the transmission line.
Higher levels of compensation (>80%) risk Ferranti effect and complex resonance phenomena.
Subsynchronous resonance (SSR) is a critical concern when k is high.
Increased power transfer capability
Improved voltage stability and regulation
Improved steady-state and transient stability
Load sharing between parallel lines
Risk of Subsynchronous Resonance (SSR)
Requires complex protection schemes (spark gaps/varistors)
High initial cost for high-voltage capacitors
Long-distance EHV transmission lines
Increasing capacity of existing transmission corridors
The range 0.3 to 0.8 is industry standard; values above 0.8 are rarely used due to protection and resonance complexity.
Option D (0.2 to 0.25) is typically too low to justify the investment cost of series capacitor banks.
A is correct — The degree of compensation in series line compensation typically ranges between 0.3 and 0.8 to balance power transfer gains with system stability constraints.
Always remember that series compensation targets the transmission line reactance (XL), while shunt compensation (like SVCs or STATCOMs) primarily targets voltage magnitude (V).