Symmetrical RMS current magnitude is typically the maximum prospective 3 phase fault level.

Maximum fault duration is typically 1 second, 3 seconds or up to 5 seconds.

**The engineer must check their project specification documents for these values.

Ambient temperature is the ground soil temperature at the depth of burial which depends on the local standards and geographical location which is typically between 15 and 40 degrees.

Maximum allowable temperature is not usually equal to the Fusing temperature but typically a much lower temperature; 250 degrees or 450 degrees are typical values.

Decrement factor is based on a conservative assumption that the AC component of the fault current does not decay with time but remains constant at its initial sub-transient value.