The power grid is the backbone of modern civilization, transmitting electricity from generating stations to industries, businesses, and homes. At the heart of this system are transmission lines, engineered to carry large volumes of power over vast distances with efficiency and reliability. Understanding the different types of transmission lines is essential to grasping how the grid functions.
Classification by Voltage:
1. Extra High Voltage (EHV) Transmission Lines – Operating above 220 kV, these lines are designed for long-distance transmission with minimal power loss. They form the primary backbone of national grids.
2. High Voltage (HV) Transmission Lines – Typically ranging from 66 kV to 220 kV, HV lines are widely used to connect generation plants with regional substations.
3. Medium Voltage Transmission Lines – Between 11 kV and 66 kV, these lines serve intercity or regional power distribution, ensuring stability at local levels.
4. Low Voltage Lines – Operating below 11 kV, they usually feed into the distribution system, bringing electricity directly to consumers.
Classification by Current:
1. AC Transmission Lines – The most widely used, owing to lower cost, easy transformation of voltage, and established global infrastructure.
2. DC Transmission Lines (HVDC) – Increasingly adopted for bulk power transfer over very long distances, underwater cables, and inter-country connections due to lower losses and higher stability.
Importance in the Grid:
1. EHV and HV lines ensure bulk transfer of power from generation hubs to demand centers.
2. Medium and low voltage lines secure the last-mile connectivity.
3. HVDC technology is paving the way for renewable energy integration and cross-border trade.
Conclusion:
The types of transmission lines, whether classified by voltage or current, collectively form a robust, layered system that rules the power grid. With innovations like HVDC and smart grid integration, transmission lines are not just carriers of electricity but also enablers of a sustainable, resilient, and energy-secure future.
