5 Types of Insulators used in Overhead Power Line

An overhead power line is used for transmitting electricity from one place to another. Insulators in overhead power lines are used to protect from any electric shock.

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An overhead electricity line is a design utilized in electric power transmission and distribution to transmit electric power across massive distances. It includes one or extra conductors suspended with the aid of towers or poles. Overhead power lines are generally the most low-cost approach of power transmission for large quantities of electric energy.


The overhead transmission lines are classified on the basis of the following:


Range of Voltage:

  • Low Voltage (LV)- less than 1000V
  • Medium Voltage (MV)- Between 1kV and 69 kV
  • High Voltage (HV)- 115 kV and 138 kV
  • Extra-High Voltage (EHV)-  from 345 kV up to 800 kV

  • Ultra-High Voltage (UHV)- Higher than 800 kV


Depending on the Length of Transmission Lines:

  • Short Transmission Line:  Length less than 60 km
  • Medium Transmission Line: Length more than 80 km but less than 250 km
  • Long Transmission Line: Length more than 250 km

There are a few types of insulators among which are Pin, Suspension, Strain, Stay and Shackle insulator. Pin, Suspension, and Strain Insulators are used in medium or high voltage applications while Stay and Shackle Insulators are mainly used in low voltage applications. 


  • Pin Insulator: The pin type insulator is utilized in energy distribution for the voltage as much as 33kV. The best advantage of the pin insulator is that it can be used vertically as well as horizontally. 


  • Suspension Insulator: The suspension type insulator is used for high voltages i.e. more than 33 kV. It consists of porcelain insulators units that are connected with each other by metal links to form a flexible string.


  • Strain Insulator: Strain insulators are used in high voltage lines. Strain insulator helps to withstand the suspension of electrical wires or cable.


  • Stay Insulator: Stay type insulators are used in low voltage line and these are to be insulated from the ground to the height. 


  • Shackle Insulator:  Used in a low voltage distribution network, this can be used in both horizontal and verticle position. It is also known as Spool Insulator. The spool insulator minimizes the breakage possibility when heavily loaded.

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