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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 relationship between the steady state change in frequency with respect to change in load is
B+R1−B
B+R1−1
B+R1−R
None of above
B+R1−1
Quick Summary: In a power system, the steady-state frequency response to a load change is governed by the system damping constant (B) and the governor speed regulation (R). The relationship is derived from the linearized steady-state power balance equation, where the frequency deviation (\Delta f) is determined by the total load change (\Delta P_L) divided by the total system frequency sensitivity (B + 1/R).
In a power system, the steady-state frequency response to a load change is governed by the system damping constant (B) and the governor speed regulation (R). The relationship is derived from the linearized steady-state power balance equation, where the frequency deviation (Δf)is determined by the total load change (ΔP_L) divided by the total system frequency sensitivity (B + 1/R).
Δf=−(B+R11)ΔPL — Steady state frequency deviation equation
D=B+R1 — Total system frequency response characteristic
When a load change occurs, the governor automatically adjusts the generation to restore balance. The total change in power is balanced by the load frequency sensitivity B (due to motor load variation with frequency) and the speed governing system sensitivity 1/R. The steady-state frequency deviation is expressed as \Delta f = -$$\frac{\Delta P_L}{B + 1/R},making the sensitivity factor equal to -1 / (B + 1/R).
R represents the governor speed regulation or droop characteristic.
B is the frequency-sensitive damping constant of the load.
A larger value of (B + 1/R) results in a smaller frequency deviation for a given load change, indicating a more stable system.
The negative sign denotes that an increase in load leads to a decrease in frequency.
Provides inherent stability to the power system frequency.
Allows for automated primary frequency control without manual intervention.
Steady-state frequency error exists unless secondary control (AGC) is applied.
Sensitivity depends heavily on the droop settings of connected generators.
Load Frequency Control (LFC) modeling.
Determination of system stability margins during load disturbances.
The parameter B is often referred to as the system damping factor, and 1/R is the governor speed regulation parameter in p.u. MW/Hz.
If the frequency bias B is ignored, the sensitivity reduces to -R.
B is correct — The steady state sensitivity of frequency change to load change is given by the negative reciprocal of the sum of the load damping and the governor response coefficients.
Always remember that the denominator is the sum of the damping factors (B + 1/R). If the question asks for frequency deviation per unit load, the answer is the negative of the total sensitivity.