Welcome to this module on LV Switchgear Construction. The visual shows 11 KV switchgear inside an indoor substation. You can also see the various low voltage switchgear panels and distribution boards housed inside the substation. This is a low voltage switchgear. The visual shows the front view. This is the rear view of the switchgear. Observe the various competence, operating handles, indicating lamps, switches, and breaker. This topic covers classification of LV switchgear based on the applications, degree of protection, construction of LV switchgear, gambling arrangements in LV switchgear, cooling arrangements in LV switchgear , forms of construction. Switchgear rated up to one kilo volt is termed as low voltage switchgear. Standard voltages are 400 volts, 415 volts, or 440 volts, three phase, and 690 volts three phase. LV switchgear, depending on the application or usage, may also be called as power control center called as BCC, motor control center called as MCC, power cum motor control center called as PMCC, UPS and distribution board called as UPS DB, DC distribution board called as DCDB, distribution board, lighting, small power. BCC receives electrical power from the secondary of the transformer and feeds to the MCCs or motor control centers. As MCCs handle bulk power outgoing feeders of BCC that feed power supply to MTCs will be ACBs. MCC. All outgoing feeders are used to supply power to motors, mostly. Each outgoing feeder meant for feeding motor is called as a starter module. PMCC, this is a combination of PCC and MCC. PCC or MCC or PMCC are floor-mounted type and are usually heavier. UPS DB feeds all loads requiring uninterrupted power supply or UPS. It may be a separate standalone panel or it may be part of UPS itself. DCDB feeds all loads requiring a direct current power supply. DC distribution board, these are having relatively smaller rating than PCC. Typically incomer could be MCCB and all outgoings are MCCBs or MCBs. DBs are usually wall-mounted type. It may also be a floor-mounting type if there are more number of feeders. DB is used for lighting, small power, auxiliary loads, space heaters, etc. Degree of protection. IP 54 is generally offered for PMCC or MCC of 1600 amperes and less for rating about 1600s amperes, IP 42 is offered. LV switchgears shall be normally installed indoors to prevent any maloperation due to dust and rainwater. Ingress protection of minimum of IP 41 shall be provided. However, manufacturers can provide up to IP 54 to meet any onerous ambient conditions. The requirement of a segregation between the three compartments, busbar compartment, switching compartment, and Gamble compartment and the IP degree of protection for desegregation depends on the level of flexibility required by the oil and emptying. The same holds good for segregation between switching compartments also. Busbars made of high conductivity, copper or aluminum are usually placed at the top in a totally enclosed compartment. Bottom most part of the switchgear shall have a base frame, which will in turn be fixed to the floor or slab. Switchgear generally comprises of three compartments. They are busbars, circuit breakers or MCCBs, or switch fuels compartments. Or we can go in a generalized way as a functional units. Gable compartment. Functions units will be placed in the middle section. Depending on space availability, one or more functional units can be pleased. Busbar droppers are used to interconnect main busbars and incomers of functional units. The connection spot of the main busbars and busbar droppers, rigid FRP shrouds are normally provided. Cable compartment may be pleased at the bottom or by the side of functional units. MCBs are usually mounted in a fixed version on a C channel called DIN rail. MCCBs, SFUs, and ACBs can be mounted in a fixed version or draw-out version. ACBs have built-in control circuitry with controlled components. With tribal ACBs will require plug and socket arrangement for connection between fixed part and withdraw viable part. Instead of a plug-in socket arrangement, it can also have a sliding contacts, as shown in the figure. The power terminals of ACB are also required to be provided with male and female type of contacts. Draw-out version usually has three positions. Service position, test position, and isolated position. Service position, both power contacts, and secondary isolating contacts, or SICs, are in a fully engaged position that is in normal working condition. Connection to the ground or earthing is retained. Test position, power contacts are disconnected and SICs, are in the engaged position. They are used for testing or troubleshooting in control circuits. Connection to the ground or, earthing is retained. Isolated position. Both the power contacts and SICs are disconnected. Under module can be moved out of the cubicle if required. The ground connection is also isolated. If the secondary contacts are connected through plugs and sockets arrangements, then they will have to be manually plugged out in isolation mode. Continue the next part.
