How Electrical Transmission Lines Work: Ohm’s Law, I²R Losses, and High-Voltage Grids | Practical Engineering

Overview

In this Practical Engineering episode, Grady Hillhouse explains why electricity often travels across great distances on high voltage transmission lines instead of staying near power plants. He walks through the physics of resistance, Ohm's law, and the I squared R losses that waste energy, and shows how stepping up voltage with transformers reduces current and improves efficiency. The video also delves into how three-phase transmission works, why towers are so tall, how insulators and air gaps provide insulation without heavy insulation around conductors, and how protective shield wires and dampers keep lines safe from lightning and wind. Finally, it touches on how solar power and distributed generation are changing the traditional grid, and how these factors influence the modern electrical landscape.

Introduction

Practical Engineering's episode on electrical transmission lines explains why power plants are not located next to every city and how the grid moves electricity efficiently across long distances.

Core Concepts

• Ohm's law and voltage-current relationships
• Power losses described by I squared R
• Voltage stepping with transformers to reduce current
• The 3-phase system and how lines are grouped

Design and Safety Considerations

• Air insulation versus thick insulation around conductors
• Tower height, spacing, and insulator discs to prevent arcing
• Insulators often use ceramic discs and the rule of thumb: count discs and multiply by 15 to estimate voltage
• Shield wires to protect against lightning
• Wind, sag, and dampers such as stockbridge dampers

Grid Evolution

The video also touches on distributed generation like rooftop solar and how changing energy marketplaces enable long-distance energy trades, reshaping the traditional transmission model.