New switchboard design standards for Australia and New Zealand

A series of standards for low-voltage switchgear and controlgear assemblies that is superseding the AS/NZS 3439 standard. These are defined as a combination of one or more low-voltage switching devices together with associated control, measuring, signalling, protective, regulating equipment with all the internal electrical and mechanical interconnections and structural parts.

This joint Australian/New Zealand Standard was prepared by joint technical committee EL-006, Industrial Switchgear and Controlgear.

There are 7 parts to the AS/NZS 61439 standard as seen below:



A major introduction in this new standard is the requirement to perform design verification which applies to all assemblies, whether they are designed on a one-off basis or fully standardised and manufactured in quantity.

The AS/NZS will be applicable from Monday 24 May 2021 and it is important to note, with the release of AS/NZS 3000 amendment 2 – also known as “the wiring rules” – it mandates the use of AS/NZS 61439 series or AS/NZS 3439 series for switchboard assemblies under the below conditions:

• The total of the connected load at the point where the switchboard is installed exceeds 125 A r.m.s per phase.


• The prospective short-circuit current at the incoming terminals of the switchboard is greater than 10 kA r.m.s.

This amendment was published prior to the effective date of AS/NZS 61439, however, since then, the AS/NZS 3439 standard has been superseded by AS/NZS 61439. This amendment has a transition period of 6 months from 30th April 2021 (date of publication).

For switchboard assemblies not included in the above conditions, they shall be suitable to withstand the mechanical, electrical and thermal stresses that are likely to occur in service, and the environment in which they are to be installed. Note that compliance with AS/NZS 61439 satisfies this requirement.

These standards have been introduced in an effort to improve safety throughout the switchboard industry while adapting to new technologies and product features. This standard is also very thorough regarding design requirements, ultimately resulting in a better-designed assembly. It also clarifies the legal and financial responsibilities between the original manufacturer, assembly manufacturer and the user in specifying, testing, designing and manufacturing assemblies.

One major change is the thorough design verification requirements. There are 13 characteristics that need to be verified, and many of these characteristics are broken down further into sections. Each characteristic needs to be verified by one of 3 methods; testing, comparison with a reference design, or assessment. The standard states which of these are appropriate for each characteristic (Annex D). These design verifications are required on every new design, and any modifications to a previously verified design.

Another change is the increased requirements of routine verification. This verification is performed to every assembly that is manufactured, which is an additional requirement to the design verification.

This standard also clarifies the information that is to be provided with the assembly as well as the requirements of the designation marking. This standard provides quite detailed requirements on these topics.

This standard applies to any switchgear or controlgear assembly regardless of the current, voltage or fault current ratings of the assembly. This includes any new assembly that you install or any compliant assembly that you modify. The AS/NZS 61439 standard is not directly mandated, however AS/NZS 3000 amendment 2 references AS/NZS 61439 in various clauses, mandating these specific requirements.

COMPLIANT MANUFACTURERS LABEL
The assembly manufacturer needs to provide each assembly with one or more labels, marked in a durable manner and located in a place that they are visible and legible when the assembly is installed and in operation. This label shall include:

• Assembly manufacturer’s name or trademark


• Type designation or identification number or any other means of identification


• Means of identifying the date of manufacture


• IEC-61439-X (the specific part “X” shall be identified)

All interface characteristics according to clause 5, where applicable, needs to be provided in the assembly manufacturers technical documentation supplied with the assembly. These include the below:

PROOF OF COMPLIANCE WITH 13 CHARACTERISTICS 

Any modifications to an AS/NZS 61439 compliant switchboard will require verification that the modifications do not affect the performance of the assembly or compliance, this includes temperature rise, clearance, creepage distances etc.

The methods for verifying compliance include:

• Verification testing
• Verification comparison with a tested reference design
• Verification assessment, i.e. confirmation of the correct application of calculations and design rules, including use of appropriate safety margins

Any modifications to an existing board not compliant with AS/NZS 61439 (installed prior to these standard being introduced) need to ensure that the modification complies with AS/NZS 61439.