Correct Answer - Option 2 : Square of current (I2
A busbar is a strip or bar of Copper, Brass, or Aluminum that conducts electricity within a switchboard, distribution board, substation, battery bank, or other electrical apparatus.
Its main purpose is to conduct electricity, not to function as a structural member.
Temperature rise in the Busbars:
During the short-circuiting, the bus bar should be able to withstand the thermal as well as mechanical stress.
The heat dissipation through convection and radiation during this short duration is negligible
All the heat is observed by the busbar itself.
T = K (I / A)2 (1 + α θ) x 10-2 °C / sec
T= Temperature rise per second
A= Conductor cross-section area
α = Temperature coefficient of resistivity at 20° C
K = constant
θ = temperature of the conductor at the instant at which the temperature rise is being calculated.
∴ The busbar temperature rise in the DG set is directly proportional to the square of the RMS value of the fault current.