The circuit protective conductor (CPC) is used to provide protection from electric shock and to allow sufficient current to flow so the protective devices can trip. Various national and international standards define the requirements for CPC. Any CPC is also an important consideration in the calculation of Earth Fault Loop Impedance.
Common types of allowable CPC include:
When considering CPC, myCableEngineering allows the following:
Note: although (3) is quite common, it is not recommended due to the difficulties in evaluating divisions of current between the armour and separate conductor.