LV distribution - centralized or distributed layout

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.

Selection guide:

• Place power sources as close as possible to the barycenter of power consumers,
• Reduce atmospheric constraints: building 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 main exists for ease of maintenance,

A layout example is given in the following diagram (Fig. D12):

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Fig. D12: The position of the global current consumer barycenter guides the positioning of power sources

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Centralized or distributed layout

In centralized layout, current consumers are connected to the power sources by a star-connection. Cables are suitable for centralized layout, with point to point links between the MLVS and current consumers or sub-distribution boards (radial distribution, star- distribution) (Fig. D13):

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Fig. D13: Example of centralized layout with point to point links

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In decentralized layout, current consumers are connected to sources via a busway. Busbar trunking systems are well suited to decentralized layout, to supply many loads that are spread out, making it easy to change, move or add connections (Fig D14):

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Fig. D14: Example of decentralized layout, with busbar trunking links

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Factors in favour of centralized layout (see summary table in Fig. D15):

• Installation flexibility: no,
• Load distribution: localized loads (high unit power loads).

Factors in favor of decentralized layout:

• Installation flexibility: "Implementation" flexibility (moving of workstations, etc…),
• Load distribution: uniform distribution of low unit power loads
  

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	Load distribution
Flexibility	Localized loads	Intermediate distribution	Uniform distributed
No flexibility	Centralized		Decentralized
Design flexibility
Implementation flexibility	Centralized	Decentralized
Operation flexibility

Fig. D15: Recommendations for centralized or decentralized layout

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Power supply by cables gives greater independence of circuits (lighting, power sockets, HVAC, motors, auxiliaries, security, etc), reducing the consequences of a fault from the point of view of power availability.
The use of busbar trunking systems allows load power circuits to be combined and saves on conductors by taking advantage of a clustering coefficient. The choice between cable and busbar trunking, according to the clustering coefficient, allows us to find an economic optimum between investment costs, implementation costs and operating costs.
These two distribution modes are often combined.