Transmission Lines and Cables Part 1
Module 3: Transmission Lines and Cables
Welcome to the third module of our power systems course, where we’ll focus on transmission lines and cables. This module is closely tied to our reference textbook, covering topics such as AC transmission lines, underground cables, and the principles behind them.
Why Transmission Lines?
Transmission lines are essential for transferring electricity from remote generation sites to population centers. With renewable energy sources often located in remote areas, the need for efficient transmission infrastructure becomes critical.
Types of Transmission Lines
We primarily discuss overhead AC transmission lines but also touch upon underground cables and HVDC lines, each with its unique characteristics and applications.
Transmission Line Structures
Transmission towers are massive structures supporting conductors and shield wires. Conductors, often aluminum conductor steel-reinforced (ACSR), are bundled to minimize electric field strength and avoid corona discharge. Shield wires protect conductors from lightning strikes.
Line Balancing and Transposition
Transmission lines may be unbalanced due to differences in conductor heights. Transposition, though costly, can mitigate this imbalance and improve system performance.
Cost Considerations
Transmission line costs vary based on factors like voltage, location, and terrain. Typical costs range from half a million to several million dollars per mile, with urban areas commanding higher prices.
Line Resistance and Skin Effect
Reducing line resistance is crucial to minimizing losses, but larger conductors increase tower strength requirements. Skin effect, caused by AC currents, concentrates current flow near the conductor surface, affecting resistance calculations.
Conductor Conductance and Corona Effect
Conductor conductance, representing loss due to corona discharge and leakage currents, is often negligible compared to other losses. It’s typically modeled in parallel with transmission line capacitance.
Conclusion
Understanding the principles behind transmission lines and cables is vital for efficient electricity transmission and distribution. By optimizing line parameters and structures, we can enhance grid reliability and reduce power losses, contributing to a more sustainable energy future.