We can control the P and/or Q transfers in the transmission line varying

Question

Examoogle · Accepted Answer

Option D: all of these

Explanation & Concepts:
Active power (P) and reactive power (Q) flow in an AC transmission line are governed by the sending-end voltage ($V_s$), receiving-end voltage ($V_r$), line reactance ($X$), and the power angle ($\delta$). By manipulating these parameters, power flow can be precisely regulated, which is the foundational principle of FACTS (Flexible AC Transmission Systems) devices.

Working Principle: The active power transfer is defined as $P = \frac{V_s V_r}{X} \sin \delta$ and reactive power flow is linked to the voltage magnitude difference. By using devices like SVCs or STATCOMs (for voltage control) or TCSC/UPFC (for impedance or angle control), we effectively modulate these variables to optimize power delivery and stability.

Key Formulas: $P = \frac{V_s V_r}{X} \sin \delta$ — Active power transfer equation; $Q = \frac{V_s}{X} (V_s - V_r \cos \delta)$ — Reactive power transfer equation

Key Points: Changing $V_s$ or $V_r$ primarily affects reactive power flow and voltage profile.; Changing the load angle $\delta$ (via phase-shifting transformers) primarily controls active power transfer.; FACTS devices act as high-speed controllers for these variables.; The impedance $X$ can also be varied using series compensation.

Advantages: Increased transmission line capacity; Improved transient and steady-state stability

Disadvantages: High initial investment costs for power electronics; Complexity in control system design

Applications: Voltage stability enhancement; Load flow control in interconnected grids

Additional Info: Voltage control is typically achieved using shunt devices like Static Var Compensators (SVC).. Angle control is typically achieved using Phase Shifting Transformers (PST) or UPFC.

Answer: D is correct — The power flow in a transmission line is a function of the voltages at both ends and the phase angle between them, all of which can be controlled to regulate P and Q.

Exam Tip: Always remember that in a lossless line, active power is largely dependent on the load angle, while reactive power is largely dependent on the magnitude of voltage differences.

Examoogle · Answer

Option A: sending end voltage

Examoogle · Answer

Option B: receiving end voltage

Examoogle · Answer

Option C: load angle

Correct Answer

Discussion (0)

Correct Answer

Related Questions

Discussion (0)