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)

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

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

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

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

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

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.

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

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

A single-line LV schematics

L.V. Switchboard

Air Circuit Breaker (ACB)