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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 transfer of reactive power over a line mainly depends upon
Vr
Vs
Vs−Vr
Power angle
Vs−Vr
Quick Summary: Reactive power transfer ($Q$) over a transmission line is primarily driven by the difference in voltage magnitudes between the sending end ($V_s$) and the receiving end ($V_r$). In a short line model, the flow of reactive power is approximately proportional to the voltage drop across the line reactance.
Reactive power transfer (Q) over a transmission line is primarily driven by the difference in voltage magnitudes between the sending end (Vs) and the receiving end (Vr). In a short line model, the flow of reactive power is approximately proportional to the voltage drop across the line reactance.
Q≈XVr(Vs−Vr) — Reactive power flow in terms of voltage magnitude difference
P≈XVsVrsinδ — Real power flow in terms of power angle δ
The reactive power flow (Q) is governed by the reactive power-voltage relationship Q≈XVr(Vs−Vr). Since the transmission line possesses inductive reactance (X), a potential difference (Vs−Vr) acts as the driving force for reactive power migration to support voltage regulation.
Reactive power is voltage-dependent, while real power is primarily angle-dependent.
A higher Vs relative to Vr forces reactive power from the source toward the load.
If Vr>Vs, reactive power flows from the receiving end back to the source.
This principle is the basis for voltage control using shunt compensation.
Provides a simple mechanism to control local bus voltage.
Allows reactive support through SVCs (Static Var Compensators).
High reactive power flow increases I2R and I2X losses.
Excessive voltage difference can lead to stability issues.
Voltage profile management in power grids.
Coordination of shunt capacitors and reactors.
Option D (Power angle) is the primary factor for active power (P) transfer.
Voltage stability is directly tied to the ability to supply sufficient reactive power to maintain the Vs−Vr balance.
C is correct — The transfer of reactive power in transmission lines is primarily driven by the magnitude difference between sending and receiving end voltages (Vs−Vr).
Remember: P (Active Power) depends on sinδ (the power angle), whereas Q (Reactive Power) depends on ΔV (the voltage magnitude difference).