Why let through energy of cable is calculated and compared against protective device let through energy, when adiabatic equation and disconnection time check is used to verify the cable sizes? or this let thru energy verification is applied only for current limiting breakers / fuses?
Though both the equations are same (just rearrangement) but the I2t value comes from the manufacturer in case of verifying the let through energy. Now my question is can we use this let through energy value (received from the manufacturer in the form of curve) to apply in this adiabatic equation
In principle you can use the manufacturer's I²t instead of the fault current I and the disconnection time t - but in general t is only available for disconnections times over 0.1s (certainly in BS 7671) - and often I²t values are only applicable for 'instantaneous' disconnection (i.e. <0.1s) - so often the choice is made for you.
Though both the equations are same (just rearrangement) but the I2t value comes from the manufacturer in case of verifying the let through energy. Now my question is can we use this let through energy value (received from the manufacturer in the form of curve) to apply in this adiabatic equation
In principle you can use the manufacturer's I²t instead of the fault current I and the disconnection time t - but in general t is only available for disconnections times over 0.1s (certainly in BS 7671) - and often I²t values are only applicable for 'instantaneous' disconnection (i.e. <0.1s) - so often the choice is made for you.
