Chapter A General rules of electrical installation design

D - MV & LV architecture selection guide
6 Choice of architecture
fundamentals
The single-line diagram can be broken down into different key parts, which are
determined throughout a process in 2 successive stages. During the first stage we
make the following choices:
b connection to the utilities network,
b configuration of MV circuits,
b number of power transformers,
b number and distribution of transformation substations,
b MV back-up generator
6.1 Connection to the upstream network
The main configurations for possible connection are as follows (see Fig. D8 for MV
service):
b LV service,
b MV single-line service,
b MV ring-main service,
b MV duplicate supply service,
b 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)
a) Single-line: b) Ring-main:
MV
LV
MLVS
Schneider Electric - Electrical installation guide 2008
MLVS
c) Duplicate supply: d) Double busbar with duplicate supply:
MV
LV
MLVS
Fig. D8 : MV connection to the utilities network
MV
LV
MV
LV
MLVS1
MV
LV
MLVS2
D15
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