Jun 02

Busbar Forms And Definitions For Switchboards Australia (protection Against Arcing Faults)

AS3000-2007 Wiring Rules – Protection Against Arcing Faults

With the introduction of the new AS3000-2007 wiring regulations, greater care needs to be taken when designing switchboards to meet these requirements and provide the enhanced level of safety.

Clause “Protection against switchboard internal arcing fault currents” states that protection against arcing fault currents while the equipment is in service, or is undergoing maintenance, shall be provided for heavy current switchboards. Heavy current circuits are regarded as those where the nominal supply current to the switchboard is 800 A or more per phase. The supply conductors within the switchboard shall have additional insulation or be segregated. In addition, the switchboard shall comply with one of the following:

(a) Clause to reduce the probability of initiation of arcing fault.

(b) Clause limit the harmful effects of an arcing fault.

(c) Both a) & b)

To reduce the probability of the initiation of a switchboard internal arcing fault, heavy current switchboards shall be provided with internal separation in accordance with AS/NZS 3439.1 for-

(a) busbars from functional units; and

(b) functional units from one another; and

(c) terminals provided for external conductors from the busbar; and

(d) a safety service circuit section of the switchboard,

This separation may be provided by the use of a Form 3b, Form 3bi, Form 3bh, Form 3bih, Form 4a, Form 4ah, Form 4aih, or Form 4b, Form 4bi, Form 4bh, Form 4bih constructed switchboard. The required degree of protection, IP2X or IP1XB,

Internal Separation along with the Degree of Protection needs to be verified as part of the type tests under Clause 8.1.1 of AS.NZS 3439.1:2002 “TYPE TESTS” Sub clause 8.1.1.(g). The Elsteel TECHNO Modular Switchboard System complies with this requirement having been certified by TEST SAFE Australia (Test Report 29540). The Degree of Protection is rated to IP55 and Internal Separation to IP2X.

To limit the harmful effects of an arcing fault it is necessary that proper calculations are done to determine the exact fault level at the point of installation and the correct protective device be used to limit the amount of energy let through in the event of a fault. Forms of internal separations

Symbols: Busbars, including distribution busbars

Form 1

No internal separation

Form 2

Separation of busbars from the units

Form 3

Separations of busbars from the functional units +

Separation of functional units from one another +

Separation of terminals from the functional units

Form 4

Separation of busbars from the functional units and terminals +

Separation of functional units from one another +

Separation of terminals associated with a functional unit from those of another functional unit

Liam Wilde Electrical Estimator Cpe Switchboards


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