Connection to the upstream network

From Electrical Installation Guide

The main configurations for possible connection are as follows (see Fig. D8 for MV service):

• LV service,
• MV single-line service,
• MV ring-main service,
• MV duplicate supply service,
• MV duplicate supply service with double busbar.

Metering, protection, disconnection devices, located in the delivery substations are not represented on the following diagrams. They are often specific to each utilities company and do not have an influence on the choice of installation architecture.
For each connection, one single transformer is shown for simplification purposes, but in the practice, several transformers can be connected.(MLVS: Main Low Voltage Switchboard)

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Fig. D8: MV connection to the utilities network

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For the different possible configurations, the most probable and usual set of characteristics is given in the following table:

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	Configuration
	LV	MV
Characteristic to consider		Simple-line	Ring-main	Duplicate supply	Duplicate supply with double busbars
Activity	Any	Any	Any	Hi-tech, sensitive office, health-care	Any
Site topology	Single building	Single building	Single building	Single building	Several buildings
Service reliability	Minimal	Minimal	Standard	Enhanced	Enhanced
Power demand	< 630kVA	≤ 1250kVA	≤ 2500kVA	> 2500kVA	> 2500kVA
Other connection constraints	Any	Isolated site	Low density urban area	High density urban area	Urban area with utility constraint

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