Chapter A General rules of electrical installation design

B - Connection to the MV public
distribution network
6 Constitution of
MV/LV distribution substations
MV/LV substations are constructed according to the magnitude of the load and the
kind of power system in question.
Substations may be built in public places, such as parks, residential districts, etc. or
on private premises, in which case the power supply authority must have unrestricted
access. This is normally assured by locating the substation, such that one of its
walls, which includes an access door, coincides with the boundary of the consumers
premises and the public way.
6.1 Different types of substation
Substations may be classified according to metering arrangements (MV or LV) and
type of supply (overhead line or underground cable).
The substations may be installed:
b Either indoors in room specially built for the purpose, within a building, or
b An outdoor installation which could be :
v Installed in a dedicated enclosure prefabricated or not, with indoor equipment
(switchgear and transformer)
v Ground mounted with outdoor equipment (switchgear and transformers)
v Pole mounted with dedicated outdoor equipment (swithgear and transformers)
Prefabricated substations provide a particularly simple, rapid and competitive choice.
6.2 Indoor substation
Conception
Figure B35 shows a typical equipment layout recommended for a LV metering
substation.
Remark: the use of a cast-resin dry-type transformer does not need a fireprotection
oil sump. However, periodic cleaning is needed.
MV connections to transformer
(included in a panel or free-standing)
2 incoming
MV panels
MV
switching
and
protection
panel
Connection to the powersupply
network by single-core
or three-core cables,
with or without a cable trench
Fig. B35 : Typical arrangment of switchgear panels for LV metering
Schneider Electric - Electrical installation guide 2008
LV connections
from
transformer
LV switchgear
Current
transformers
provided by
power-supply
authority
Transformer Oil sump LV cable
trench
B37
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