Why Crushed Rock is used at the earth surface in the substation?

  • We always see crushed rock spread on the surface of soil in the substation. 
  • The resistivity of gravel is approximately 2000 ohm – meter whereas the soil resistivity is only 100 ohm – meter. 
  • We say that the resistivity of gravel is 20 times than that of soil. 
  • The gravel acts as an insulator and back the electric field by the Ground potential rise ( GPR ).

Advantages of Crushed Rock over Soil
  • It provides high resistivity at the surface
  • Growth of weeds not possible
  • People don’t run in the switchyard therefore risk of step potential is reduced
  • Reduce moisture of the soil
  • Minimize the hazards caused by the movement of reptiles

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