Tasharraf da kadan kusa ko kusan kadan kusa
Duk da karamin kasa na iya hankali zuwa 1KV ana magana a cikin karamin kasa ta tsakiyar. An sani LV Karamin Kasa ya haɗa da karamin kasa ta tsakiyar circuit breakers, switches, off load electrical isolators, HRC fuses, earth leakage circuit breaker, miniature circuit breakers (MCB) da molded case circuit breakers (MCCB) waɗanda suka fi shi ne don kaɓaƙar kasa ta tsakiyar. Ainihin da ake amfani da ita a cikin LV karamin kasa shine LV distribution board. Wannan system yana da abubuwa masu
Incomer
Incomer yana ba da karamin kasa na iya taka zuwa incomer bus. karamin kasa da ake amfani da ita a cikin incomer ya kamata ya samun wurin ɗaya. Abubuwan karamin kasa da ake gudanar da incomer suka fi son in ba da kyau don koyar da karamin kasa ta tsakiyar. Amma ya kamata ya zama da kyau don koyar da karamin kasa ta tsakiyar. Yana da interlocking arrangement da downstream devices. Duk da air circuit breakers suna da muhimmanci a kan hakan. Low voltage air circuit breaker yana da muhimmanci saboda abubuwan
Simplicity
Efficient performance
High normal current rating up to 600 A
High fault withstanding capacity upto 63 kA
Saboda air circuit breakers suna da lokacin da ke tsakiya, mai girma, da kuma kadan karkara, amma suna da muhimmanci a cikin karamin kasa ta tsakiyar saboda abubuwan da aka bayyana.
Sub – Incomer
Wadannan sub-incomers suna taka karamin kasa daga main incomer bus kuma suna bari wannan karamin kasa zuwa feeder bus. Abubuwan da ake gudanar da sub-incomer suka fi son in ba da kyau don koyar da karamin kasa ta tsakiyar.
Ability to achieve economy without sacrificing protection and safety
Need for relatively less number of interlocking since it cover limited are of network.
ACBs (Air Circuit Breakers) da switch fuse units suna da muhimmanci a cikin sub-incomers da molded case circuit breakers (MCCB).
Feeders
Duk feeders suna taka karamin kasa daga feeder bus don koyar da duk abubuwan da suka taka karamin kasa, motor, lighting, industrial machinery, air conditioner, transformer cooling system, etc. Duk feeders suna da muhimmanci don koyar da karamin kasa ta tsakiyar. Za a yi bayanai
Motor Feeder
Motor feeder yana da muhimmanci don koyar da over load, short circuit, over current up to locked rotor condition and single phasing.
Industrial Machinery Load Feeder
Feeder connected industrial machinery load like oven, electroplating bath etc are commonly protected by MCCBl and switch fuse disconnector units
Lighting Load Feeder
This is protected similar to industrial machinery load but additional earth leakage current protection is provided in this case to reduce any damage to life and property that could be caused by harmful leakages of current and fire.
A cikin LV karamin kasa system, electrical appliances suna da muhimmanci don koyar da short circuit and overload conditions da electrical fuses or electrical circuit breaker. Amma, operator ba sa ba da muhimmanci don koyar da faults occurs inside the appliances. Yana iya koyar da wannan problem ta haka da amfani da earth leakage circuit breaker. Wannan yana operate on low leakage current. Earth leakage circuit breaker can detect leakage current as low as 100 mA and is capable of disconnecting the appliance in less than 100 msec.
A typical diagram of low voltage switchgear is shown above. Here the main incomer comes from LV side of an electrical transformer. This incomer through an electrical isolator as well as an MCCB (not shown in the figure) feeds the incomer bus. Two sub-incomers are connected to the incomer bus and these sub-incomers are protected by means of either switch fuse unit or air circuit breaker. These switches are so interlocked along with bus section switch or bus coupler that only one incomer switch can be put on if bus section switch is in on position and both sub incomer switches can be put on only if bus section switch is at off position. This arrangement is fruitful for preventing any mismatch of phase sequence between the sub – incomers. The different load feeders are connected to any of both sections of the feeder bus. Here motor feeder is protected by thermal overload device along with conventional switch fuse unit. Heater feeder is protected only by conventional switch fuse unit. The domestic lighting and AC loads are separately protected by a miniature circuit breaker along with common conventional switch fuse unit. This is most basic and simple scheme for low voltage switchgear or LV distribution board.
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