To understand how to design an advanced DCC Track power system for a large layout, one must break down the electrical system into smaller modular "Building Blocks". The purpose of this section is to define each section and where it fits into the overall plan. The system is not unlike an upside down tree with the booster at it root. Multple booster form multiple trees side by side in a row.
1) BOOSTER DISTRICTS
All the track that is powered by a single booster. This term is only useful when the given layout have MORE THAN ONE booster. In such cases where there is only one Booster District, we simply say booster.
A given booster district can feed multiple POWER DISTRICTS or be the Power District.
2) POWER DISTRICTS
A section of track that is powered by a DCC short circuit protection device. The most common short circuit protection device is a DCC Circuit Breaker. But it can also be a light bulb or any device that shuts down or limits current hen excessive current is drawn.
The Power District device gets its input power from a single Booster or a specific Booster District Booster.
Multiple Power Districts allow one to contain or control the extend of a DCC power loss due to a short circuit in a given area protected by the Power District device. It job is to shutdown or cutoff the offending overload or short circuit before the booster does so that other parts of the layout remain running.
There is no purpose in creating a single Power District with only one booster. A booster is a single power district all by itself. Stated another way, if you going to set up Power Districts, you must have more than one for there to be any potential benefit of having them in the first place.
3) TRACK BUS
Each Power District reaches the track though the Track Bus. A Track bus is the two wires that carry the DCC current that will end up on both rail powering a given train.