Automatic Voltage Control (AVC)

Objectives
• Understand the purpose of Automatic Voltage Control (AVC) in transmission and distribution.
• Learn about AVC schemes for transformers with on-load tap changers (OLTC).
• Review line drop compensation (LDC) and circulating current principles.

Key Topics
• Purpose: Maintaining customer supply voltage within statutory limits and managing reactive power (VAR).
• AVC Relay Functions: Tap change control, voltage setpoint, bandwidth, time delay.
• Line Drop Compensation (LDC): Compensating for voltage drop along a feeder.
• Parallel Operation of Transformers: Master-Follower, Negative Reactance, and Circulating Current methods to prevent hunting.
• Interface: AVC relay connections to VT and OLTC control circuits.

Practical Focus
• Setting calculation exercise for an AVC relay with LDC.
• Reviewing a scenario of two transformers operating in parallel with a master-follower scheme.

Suggested Diagrams
• Single line diagram showing a transformer with an OLTC and its associated AVC control loop.
• Phasor diagram illustrating the principle of Line Drop Compensation.

Key Takeaways
• Understanding of voltage control philosophy in power networks.
• Ability to review AVC schemes and their impact on system performance.

Standards & References
• Engineering Recommendation G74 (UK) – Voltage control.
• IEC 60076-21 – Tap-changers.
• Various utility-specific technical specifications for AVC.

Certification & Delivery
• Certificate of Completion awarded.
• Delivery Mode: Online (On-demand).
• Corporate and customized training available on request.