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HK

ABB

03-01

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Low VoltageSwitchboard design

problems in Hong

Kong

Ir C. H. Fung

Tel 29293701

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Normal switchboard design procedures !

n Read the single line diagram / schematic diagram

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Normal switchboard design procedures !

n Check the switch Room size

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n Which supplycompanies will beconnected, HEC or CLP

n Which IDMTcharacteristic will be

installed

n Check the

specifications

Normal switchboard design procedures !

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Normal switchboard design procedures !

n Code of Practice forthe electricity

(wiring) regulations

n Supply rules of theCLP / HKE

n BS, EN or IEC

standards

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Switchboard design : draft preparation

n Put all the switchgears into the

cubicles according to the

schematic diagram

n A switchboard draft finished

n Prepare the busbar routing

according to the schematic

n

Note the form of segregationof the cubicles

n Busbar size, CT chamber,

KWH location, Change Over

switch.

Switchboard Draft before prepare the formal drawings

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Switchboard design: fine tune the design

n Try to put the switchboard into

the switch room

n Clear maintenance access as

specified in the EMSDs COP(Front = 900mm, Rear =

600mm)

n Note the Cable/ Busbar from

the supply comnpanyn Note the supply cos phase

sequence

n Note the CT Chamber size

and 600mm min. 2600mm

max AFFL

C. T. Chamber

Switchboard in factory

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Switchboard design-3

n Note the size of the KWH

meters installation

n Note the incoming cable

routing and reserve enough

space and bending radius for

cable and busbar entry

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Specification-1

n 50KA 3sec for 2500A, 2000A, 1600A, and

1250A busbar and its associated components.

n 50KA 3 sec for 800A and below is impossible

n Type Tested Assembly (TTA) to IEC or BS

standard is hard to comply.n Extension of Busbar at both side of the

assembly in a small switch room is waste of the

material and not feasible

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Specification- Functional units

n Functional Units located between 400mm and

1800mm AFFL is difficult to comply if the switch

room is small

n ACB should be Solenoid operated is for OLD design

ACB. Nowadays, ACBs are motorised

n

Oil Dash-Pots overload protection is applicable tothe ancient ACB or can be found in the Museum

n Double break Isolator is hard to find in the market

n

50KA 1 sec MCCB is impossible to comply

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Specification- IEC 60439-1 Page 1

n 7 Type Tests

n Temperature rise

n Dielectric test

n Short Circuit Test

n Effectiveness of the protective circuit

n Clearance and Creepage distances

n Mechanical Operation

n Degree of Protection

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