A `Power District’ is that part of a layout controlled and supplied by a single Command Station or Controller.
Where the power requirements for a layout exceed the maximum power output of a Command Station (about 5A) or the Controller (about 1A) but it is still required to control that `District’ then additional power is supplied through a Power Booster, in the case of a DCC layout or by switching off power to those areas not in use. In this case, the overall `Power District’ has to be sub-divided into `Sub-Districts’, ‘Track Sections’ or Blocks’.
A `SHORT CIRCUIT’ or a `SHORT’ as it is more commonly known – anywhere within a `Power District’ or `Sub-District’ will bring that entire `District’ or `Sub-District’ to a sudden halt until the short is cleared.
This is not an ideal situation, especially for an `exhibition’ layout. To overcome this problem, the `Sub-Districts’ can be further sub-divided into individual `TRACK SECTIONS’ and as you will see shortly, this breakdown into smaller, more manageable chunks comes in very handy when we look at the problems encountered when trying to control our layout.
To overcome the problem of a ‘short’ circuit bringing down an entire Power District - your layout – we can split the Power District down into smaller, more manageable pieces we call `Sub-Sections’ and ‘Track Sections’.
A ‘Track Section’ is an electrically isolated section of track.
Each ‘Track Section’ has its own feed that we protect in some way so that when a ‘short’ does occur in any section then only that Section with the short circuit is affected and the rest of the sections are left to carry on as if nothing was wrong.
Just as we split down the whole layout into `Power Districts’ following some logical process – every station, goods yard, the `up’ and `down’ main lines – so we can split these into these smaller, more manageable, bite-size, zones that we call ‘Sub-Sections’ and ‘Blocks’.
For example, every siding off a point forms one ‘Block’, since you cannot run another locomotive in the section where you have a de-railment and therefore a short circuit.
Another example of a suitable place to split would be the platform roads and the run-around loops within the station.
Look at your layout and you will begin to see where you can break down these bigger ‘Power Districts’ into smaller ‘Sub-Power Districts’ and the ‘Track Sections’ into more manageable ‘Blocks’.
Each `Track Section’ is electrically isolated from its neighbour by using insulating fishplates on BOTH rails at the `Section’ boundary.
This also applies at `Power District’ boundaries and where `Reverse Loops’ are used.
The Upstairs Layout has been broken down in this manner . . .
The Upper Level is made up of three sections – the ‘Up’ and ‘Down’ main lines and the Reverse Loop since the Reverse Loop connects to both the UP and DOWN main running lines.
The Upper Level Station has passing loops to hold stopping trains whilst allowing passing trains to operate.
The Lower Level is similarly divided with passing loops on both lines to hold trains as well as a set of Reception Sidings.
The Main Terminus Station on the Lower Level is also split into two sections – the ‘IN’ and ‘OUT’ lines. It is further divided down into the Platform Roads, the Goods Sidings and the Engine Shed.