€1,",) JM Switchboards 3) MSwichoourds May 26,2020, & min ead Switchboard Forms of Segregation Explained ‘Bo you fel out of your depth when people stat talking about forms of segregation, such as Form 38 or Form 4ain? 2 == = —: “fe ie |= | | = oS BB an | @ @ a ‘o To pati simply these are the methods for internally separating the functional units ana busbars ofan Assembly, 2s speci ty AS/NZS 61439, ‘The & main categories outlined by the stancard are Form Form 2 Form 3 Form 4 Te composi the ormsinreases wth the numbers Key definitions Acsenbly Refers to 2 switenboard which contains \etveltage control and switengeat Functional unit Partot an Assembly comprising ll the electrical and mechanical elements including switching devices that contribute to the flfiment of the same function 9.2 motor starter aster Refers 102 low-impedance conductor to which several elec eeuits ean be Separately connected. The term “ousbar’ does et presuppese the geometrical shape size,or dimensions cf the conductor. ‘Symbols UsedFAR same Funan Teas sae ce ce Form 1 ‘A switenboard with no internal separation Busbars terminals for outgoing cables and al functional units are installed ona single contra section. Form 1 sgregation is suitable for small, ewer power switehboards, Form 2 ‘The busbars and functional units are separated and broken down into another 2 categories ~ Form 2a and Form 2b ‘+ Form 29 External cabling terminals are not separated from the busbar. + Form 2b External cabling terminals are separated from the busbar.‘There are several advantages to segregating funcional units and busbars, net east of which is safety Ths model allows circuit breakers be reset when ‘the switchboard is live because the operator is net exposed toa lve busbar Form 3 ‘Things start to get more complicated from here. As with Form 2, busbars and funetional units are segregated. Functional units are also separated from each other in cubicles, and terminals are then separated from functional units, but they are not segregated from other functional units’ terminals. Thisis also broken down into? categories + Form 3a~ External cabling terminals are nt segregated from busbars ‘+ Form 3b External cabling terminals are separate trom busbars Frm 3b is frequently required fo MCC basically means that busbars and each motor starter are installed within their own cubicles. The advantages Include safety ease of maintenance and reliability because its possible to isolate and perform maintenance on each starter witraut having to power down ‘the whole switchboard, Serious faults within a starter are also mere likely tobe contzined within 2 cubicle meaning adjacent starters are unaffected and can ‘rate normally, All hese advantages come at 2 cost a5 aForm 3 beards significantly bigger and more expensive than 2 Form 1 er? board, Form 3 segregation i ypealy used for mining projects and larger operations that have asubstartia nursber of toads, motors and critica processes. They are utised when safety, relabilty an limited downtime are crucial, Form 4 ‘This is the highest form rating, as specified by AS/NZS 61439.1. With Form 4, busbars are separated from functional units and external cabling terminals. Functional units are further separated from each other, and from the external cabling terminals for each functional unit. As withthe other forms, ths is dvd into 2 sub-categories: + Form 4a~ External cabling terminals are within the same cubicle as the corresponding functional unt.+ Form db—The external cabling terminals are rot inthe sare cubicle asthe corresponding functional unit, and they are separated trom the terminals af ther funetional units ‘The major aiference between Forms 3 and & isthe separation ofthe terminals of each functional unt the terminals of ether unis. The main advantage of ‘his models the abilty safely connect and disconnect outgsing cables while the rest ofthe switchbcard ramains in operation ‘The high cost ofthis rating means that Form 4 fs usually only used in hospitals o for eitical industrial processes, Segregating the | and H Mette ornen-neaic brs are typical vedo searegat neon unis erinals ane busbars ad achieve he erm rings cine above This reas eaunment is ouse separate ables thn smtcooarStndass, however grove ther metheds o be used for segregation whieh ae Coser and cheaper such 5 ising the ntegrl camparment a furctoa\ an and insulating ermal or bsoars Using Integral Housing Irs functional unit's housing consis ith protection standards IPDX(sfingersies ject cannot come into contac with ay ve ports, canbe used to separate functional unt rat elsing busbar. This method is sed only fr segregating functional unis rom one another and therefore applies ony to Forms and 4 ‘This method is ientiles by adding 2h tothe form rating, Far example, Form 3b, Insulating busbars or terminals Insulation canbe utlsed to separate bsbars frm both funetonal units and terminals tis ls possible to shroud terminals for segregation fromthe ‘anctiona\ nits of ther terminal ‘The use ofthis method ois identified through the incision of tothe form rating. tis used fe ereate 2b, 3b and Ab Combining insulation and housing Component heusings and nsulation cn be used together frinterna segregation. The combined use ofthese methods i ented trough te inclusion of an tothe forms. This methods used to achieve forms i, Gah and din, ‘As noted, tne use of "and "h"is a cheaper method to achieve form ratings It should also be considered inferior to tne use of physicel barriers to achieve form catngs