LV distribution - centralized or distributed layout
Position of the main MV and LV equipment on the site or in the building.
This layout choice is applied to the results of stage 1.
As recommended in IEC60364-8-1 §6.3, MV/LV substation location can be determined by using the barycenter method:
- taking into account service conditions: in dedicated premises if the layout in the workshop is too restrictive (temperature, vibrations, dust, etc.)
- Placing heavy equipment (transformers, generators, etc.) close to walls or to main exits for ease of maintenance.
A layout example is given in the following diagram (Fig. D13):
Centralized or distributed layout of LV distribution
In centralized layout, each load is connected directly to the power source. (Fig. D14):
In distributed layout, loads are connected to sources via a busway. This type of distribution is well adapted to supply many loads that are spread out, where easy change is requested or future new connection (need of flexibility) (Fig. D15):
Factors in favour of centralized layout (see summary table in Fig. D16):
- Installation flexibility: no,
- Load distribution: localized loads (high unit power loads).
Factors in favor of distributed layout:
- Installation flexibility: "Implementation" flexibility (moving of workstations, etc…),
- Load distribution: uniform distribution of low or medium unit power loads
|Flexibility (see Installation flexibility for definition of the flexibility levels)||Localized loads||Intermediate distribution loads||Uniformly distributed loads|
|Flexibility of design|
Centralized distribution gives greater independence of circuits, reducing the consequences of a failure from power availability point of view.
The use of decentralized distribution with busway is a way to merge all the circuits in one: it makes it possible to take into account the diversity factor (ks), which means cost savings on conductor sizing (See Fig. D17). The choice between centralized and decentralized solutions, according to the diversity factor, allows to find an economic optimum between investment costs, installation costs and operating costs.
These two distribution modes are often combined.