This myCableEngineering software FAQ answers common questions about earthing, earth return paths and user defined cable ratings.
Earthing
Earth Return Paths
The earth return paths include all (armour, screen, etc.) but not any path through the earth or ground. This is extremely complicated to calculate, would require additional information and any resultant value would be significantly large compared to any other return path.
If you are noticing high values of R2 or Z2, please ensure that you have specified some form of metallic earth return path.
Cable Sizing
When should I use User Defined Rating (UDR)?
Use User Defined Rating when the sustained current capacity of the cable has been determined outside the standard sizing tables available in myCableEngineering. This may be appropriate where the rating comes from a manufacturer’s datasheet, a project-specific calculation, a specialist installation method or another recognised engineering assessment.
When using UDR, enter the current rating, the conductor operating temperature and the conditions that apply to that rating. The value is then used by the software for downstream checks such as voltage drop, impedance and fault-rating calculations.
For most cases, you will want to select a sizing standard from the dropdown box. This will allow you to size and determine the correct CSA for your cable.
For broader navigation help, return to the software help overview. For the engineering background, see earth fault loop impedance.