Types of Transmission and Distribution Lines Based on their Primary and Secondary Roles

Types of Transmission and Distribution Lines Based on their Primary and Secondary Roles

  1. Primary Transmission Lines:

    • Purpose: Primary transmission lines are the backbone of the electrical grid, responsible for carrying bulk electricity over long distances from power plants to substations.
    • Voltage Levels: They operate at very high voltages, typically 66 kV (kilovolts) and above, to minimize energy losses during transmission.
    • Construction: These lines are constructed using robust materials such as steel towers or concrete poles to support high-voltage conductors.
    • Examples: Extra High Voltage (EHV) transmission lines, typically operating at voltages of 220 kV, 400 kV, or even higher, depending on the distance and power capacity requirements.
  2. Secondary Transmission Lines:

    • Purpose: Secondary transmission lines serve as a link between substations and primary distribution networks, helping to transmit electricity from high-voltage substations to lower-voltage distribution substations.
    • Voltage Levels: They typically operate at medium voltages, such as 33 kV, 66 kV, or 132 kV, depending on the specific requirements of the distribution system.
    • Construction: Secondary transmission lines may use smaller towers or poles compared to primary transmission lines but are still designed to handle significant power loads over moderate distances.
    • Examples: Sub transmission lines, which connect primary substations to distribution substations, or interconnection lines between different parts of the transmission network.
  3. Primary Distribution Lines:

    • Purpose: Primary distribution lines distribute electricity from substations to larger consumers, including industrial facilities, commercial complexes, and large residential areas.
    • Voltage Levels: They operate at medium voltages, typically ranging from 11 kV to 33 kV, depending on the specific requirements of the distribution network and the size of the consumer base.
    • Construction: Primary distribution lines may use smaller conductors and support structures compared to transmission lines but are designed to handle significant power loads over shorter distances.
    • Examples: Lines supplying electricity to industrial parks, commercial centers, or large residential neighborhoods.
  4. Secondary Distribution Lines:

    • Purpose: Secondary distribution lines deliver electricity from primary distribution lines to individual consumers, including residential homes, small businesses, and institutions.
    • Voltage Levels: They operate at lower voltages, typically ranging from 120 volts to 480 volts in residential areas and 240 volts to 600 volts in commercial areas.
    • Construction: Secondary distribution lines use smaller conductors and support structures suitable for delivering electricity directly to end-users.
    • Examples: Lines running along streets or through neighborhoods, connecting to individual homes and businesses.