Chapter A General rules of electrical installation design

D16
© Schneider Electric - all rights reserved
D - MV & LV architecture selection guide
Characteristic to
consider
Configuration
LV MV
For the different possible configurations, the most probable and usual set of
characteristics is given in the following table:
Simple-line Ring-main Duplicate supply Duplicate supply
with double
busbars
Activity Any Any Any Hi-tech, sensitive
office, health-care
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
a) Single feeder: b) Open ring, 1 MV substation:
MV MV MV MV MV
LV
MLVS 1
LV
MLVS n
Fig. D9 : MV circuit configuration
LV
MLVS 1
6 Choice of architecture
fundamentals
Schneider Electric - Electrical installation guide 2008
High density
urban area
6.2 MV circuit configuration
Any
Urban area with
utility constraint
The main possible connection configurations are as follows (Fig. D9):
b single feeder, one or several transformers
b open ring, one MV incomer
b open ring, 2 MV incomers
The basic configuration is a radial single-feeder architecture, with one single
transformer.
In the case of using several transformers, no ring is realised unless all of the
transformers are located in a same substation.
Closed-ring configuration is not taken into account.
LV
MLVS 2
LV
MLVS n
c) Open ring, 2 MV substations:
MV
LV
MLVS 1
MV
LV
MLVS 2
MV
LV
MLVS n