What is Switchgear?
The apparatus used for switching, controlling and protecting the electrical circuits is known as switchgear. LV switchgear rated voltage is below 1000V
Switching actions like making and breaking of electric circuits, For example switching ON/OFF of incomers and outgoing feeders using Circuit Breakers, Switch fuse unit, contractors etc.
Controlling and Protecting actions like over-current, over-voltage, under-voltage, identification of faults etc. Current transformers(CT), potential transformers(PT), protective relays, and associated circuitry, that monitor, control and protect the electrical conducting components.
Switchgear Incomer Scheme
Switchgear with incomer scheme can be of Three types:
- Single incomer : Switchgear is fed from one transformer.
- Double incomer : Switchgear is fed from two transformer and has redundancy. On failure of one transformer, second transformer are selected in such a way it will take over the 100% load of the switchgear.
- Triple Incomers: Switchgear is fed from two transformer and has redundancy. Each transformer are selected to carter 50% load of the switchgear, On failure of one transformer, third transformer will take over the 50% load of the switchgear.
What are MCC, PCC and PMCC
MCC stands for Motor Control Center : This switchgear outgoing feeder are mainly Drives(LV Motors).
PCC Stands for Power Control Center : This Switchgear outgoing feeders are distributing further to downstream distributing panels and there are no drive(Motor) feeders.
PMCC stands for Power cum motor control center : This switchgear outgoing feeders are combination Drives(Motors) and feeders which are further distributing to downstream distributing panels.
Switchgear busbar are fed from Transformer secondary by means of Bus duct or cable, this incomers can be single incomer or double incomer or triple incomer. Incomer of switchgear will have circuit breaker, interlocks with tie breaker and protection system.
Tie breaker will be applicable when switchgear is having 2 or 3 incomers, which is normally open so that if one Transformer/source fails, the Tiebreaker can be closed and the second source will be utilized for loading all the loads in both busbars. Tiebreaker scheme is a very popular and reliable system.
Outgoing feeder can be different type mainly like motor feeder(protected against over load, short circuit ), Lighting Load Feeder(commonly protected by MCCB and switch fuse units), distribution feeders( (commonly protected by MCCB and switch fuse units )