Transcript Switchroom and Switchboard

Consumer’s Main Switchroom &
Main L.V. Switchboard
• Learning outcome from this topic, the
student is able to
– state the functions and requirements of a main
switchroom
– state the functions and requirements of a main
switchboard
– sketch a single-line LV supply diagram from a
main switchboard to different parts of a building
– describe different tests for a switchboard (the
type tests and routine tests)
1
Consumer’s Main Switchroom
• General requirements for main switchroom
– Sufficient space for work and to house the main
switchboard and other distribution equipment (600mm
for switchgear ≤ 100A, 900mm for those >100A)
– Next to transformer room
– Supply taking from a LV network, the room should be
at the building entrance
– Clear access
– Good ventilation
– Minimum illumination: Floor – 150 lx, wall: 120 lx
– No water or drainage pipes inside
2
Consumer’s Main Switchroom
• Function of a main switchroom
– power is taken from a transformer room
– power distribution to different parts of a
building and for different usages
– separate the consumer side from the
power company
3
Layout of cubicle-type main
switchboard
• Components in a main switchboard
– Body built with 2 mm-thick steel and coated with
suitable paint
– A busbar compartment with hard drawn copper and
high conductivity to BS1432 or BS1433
– Compartment for the incoming and outgoing cables
– Neat internal wiring and with sufficient clearance
– A compartment housing ACB, MCCB, fuseswitch,
motor starter, capacitor bank, auto-changeover switch
– A meter compartment to show the energy consumption
or maximum demand
4
Layout of cubicle-type main
switchboard
• Components in a main switchboard
– Measuring CTs and protection CTs
– Meters showing current, voltage, power factor (and
max. demand), etc. Now A digital multi-purpose is used
for all
– IDMT relays for overcurrent and earth-fault protection
(Now a digital relay)
– Charger and battery for closing/tripping of ACBs
– Phase indication lamps
– Anti-condensation heaters
– Spare compartments
5
Layout of cubicle-type main
switchboard
• The main switch in a switchboard
– For three-phase 4-wire supply, a triple-pole &
neutral (TP&N) main switch (or circuit breaker)
is used
– The TP&N switch should interrupt all the
phase conductors (R/Y/B)
– A link (fixed by bolts or screws) should be
inserted in the neutral conductor
– For single-phase installations, a double-pole
(DP) main switch should be used
6
Layout of cubicle-type main
switchboard
• If the supply is taken directly from a transformer
room, the main incoming ACB
– should be of draw-out type
– should have a breaking capacity at least 40 kA
– should be equipped with overcurrent & earth-fault
protective relays
• For an overall installation serving more than one
building, the installation in each building should be
treated as a separate installation. Each building
should have a main switch.
7
Load Distribution in a Building
• Refer to slide 10 for illustration
• Tenant Supply Board
– Connection to a transformer
– Main incoming circuit breaker (ACB/MCCB) for overload and
fault protections to the whole installation
– Busducts leading to different load centres in the building
– Bus section switch interconnects adjacent busbar section
• Non-essential Public Supply Board
– Bus section for the power supply to public facilities
• Plumbing and drainage pumps, passenger lifts, non-essential
lighting, A/C plant and spares, etc
– Cable risers to different loads in the building
– Protective devices for cable overload protection
– Bus section switch interconnects adjacent busbar section
8
Load Distribution in a Building
• Emergency Supply Board
– Connection with an emergency generator / UPS
– ACB, MCCB, fuseswitch for overload and / or fault
protections to essential loads
– Automatic changeover switch
• Two mutually exclusive switches
– Normal open (N/O)
– Normal close (N/C)
• Switch ON/OFF
– Sprinkler pumps, hydrant / hose reel pumps,
firemen’s lifts, emergency lighting and spares, etc
• A single-line low voltage schematic for the
power distribution to different loads in a building
is shown on slide 11
9
A single-line LV schematics
10
L.V. Switchboard
11
Air Circuit Breaker (ACB)
12
13
14
15
16