loola said:
Hi
I need some help!! Can anybody explain the operations of the following components of an electrical distribution system please?
Main Consumer Unit
Residual Current Device
Catridge Fuse
Earth Wire
Thanks!!
Main consumer unit
The first point in the 'electric chain' of any household electricity supply. From here all other circuits are fed and protected by the fuses/MCB's/RCD's.
RCD
A device that measures the current flowing through the phase and neutral conductors and when an imbalance is detected that exceeds the rated trip value the supply is turned off.
Catridge Fuse
A cartridge which accepts rewirable fuse wire. Connected to the consumer unit it's purpose is to break the supply in the event of an overload. This overload depends on the value of fuse wire installed in the cartridge fuse.
Earth Wire
Takes many forms including:
the main equipotential bonding conductors that connect the gas and water supply pipes to the main earthing terminal
supplementary bonding conductors that link conductive metal parts in bathrooms
the main earthing conductor connecting the main earthing terminal to the earthing point.
the earth cable as part of sheathed cables.
In all cases its used as a path for fault current (except supp. where its used to limit P.d between conductive parts to reduce the risk of shock) Earthing is needed to allow a large enough current to flow from phase to earth so that the protective devices can activate so as to remove the danger.
You might want to read the regs for the actual 'text-book' answers as what I've written will not contain all the info you need to answer your questions.
Davy