Design Stage

[Bright_Spark]

hi all

could someone please explain to me why i need the follwing information at the design stage of an istallation -

- Prospective earth fault current (I)
- The value of external impedance (Ze)
- Assumed current demand of the installation
- Disconnection times of certain light fittings

Many thanks

 

[Darkwood]

Is this for revision purposes in which case your answers need to be specific or you happy with us to throw our thoughts to it.

 

[Bright_Spark]

its for revision so i need reasons to the answers and not just answers please, i need to understand why, not just be given the answers, thanks

 

[Darkwood]

its for revision so i need reasons to the answers and not just answers please, i need to understand why, not just be given the answers, thanks

Did my exams 20 yrs ago so although ive a good idea why il leave this one to someone doing the same courses as yourself and can word it as the tutor expects.

 

[barx]

At design stage you ned to specify protective devices. PFC will tell you what breaking capacity is required for the devices. Ze (And you proposed circuits) Could effect what type of device is chosen. i.e. max efli for type c breakers is half that of type b. Assumed demand to make sure supply is adequate. Disconnection times - again to do with devices and this time cable size too. breakers need to trip quick enough to meet the requiments.

 

[Spudnik]

Moved to the courses forum