Key Points



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Key Points

 

The Electrical Safety Act takes precedence over any standard

  • As an example, for Victoria clause 54 states: "A person must not supply or offer to supply electrical equipment unless - (a) the equipment complies with the minimum standards prescribed for equipment of that class;"" Therefore, all switchboards are required to satisfy a switchboard standard, including smaller boards; however, in AS/NZS 61439 the requirements are dependent on ratings i.e.
  • Short circuit verification is not required under 10kA or 17kA when protected by current-limiting devices
  • Temperature rise limit verification by calculation may only be completed for assemblies not exceeding 1600A (or single compartment ASSEMBLY not exceeding 630A)drawing

AS/NZS 61439 has 8 parts:

  • Part 0 - A guide for specifiers to be used at tender
  • Part 1 - General rules
  • Part 2 - Low voltage switchgear and control gear assemblies
  • Part 3 - Distribution boards intended to be operated by ordinary persons
  • Part 4 - Assemblies for construction sites
  • Part 5 - Assemblies for power distribution in public networks
  • Part 6 - Busbar trunking systems
  • Part 7 - Marina, camping, market and charging

Should an assembly manufacturer deviate from the original manufacturer documentation, then the assembly manufacturer is deemed to be the original manufacturer in respect of those arrangements.

If a user accepts a switchboard without verification to one or more characteristics in Annex D, then they are at risk of being financially and legally responsible for any issues that may arise.

Verification by comparison to a reference design requires demonstrating that the new characteristics are the same or better than the tested design.

The "In-Country Notes" that modify IEC 61439 to AS/NZS 61439 only affect the Assembly Manufactures requirements. Therefore any Original Manufacturers test documents to IEC 61439 may be used to support the assembly manufacturers verification assessment of the switchboard design to AS/NZS 61439.

Test certification to AS/NZS 3439 may be used for verification characteristics to AS/NZS 61439 only if the test methods required are the same. For example:

Short circuit tests remain the same and may be used

Heat rise test requirements differ, therefore may require further testing

 

What are the main differences between AS/NZS 3439 (Old) and AS/NZS 61439 (New)

 

Area of Difference AS/NZS 3439 (OLD) AS/NZS 61439 (NEW)
Term for a compliant switchboard              Type Test (TT) & Partial Type Test (PTT) Design Verified (TT & PTT no longer used)
Heat rise testing              May be undertaken in "Free Air" Must be completed as a complete system 1)
Temperature limits of copper conductor ΔT of 70K above a mean ambient of 35°C

ΔT of 105K from a mean of 35°C

Therefore, a maximum theoretical mean of 140°C on the copper 2)

Heat rise calculation using IEC 60890 Allowed up to 3150A For a single compartment ASSEMBLY not exceeding 630A or for ASSEMBLIES not exceeding 1600A             
Device substitution Undefined Undefined

 

1) Testing with all covers fitted and electrical components connected.
2) ΔT of 105K is specified in the standards as this is the maximum temperature rise before copper starts to anneal. This theoretically could allow a maximum absolute temperature of 140˚C on the copper busbar. However, as under the new standard tests must be conducted as a complete system, other temperature limits will be reached before 140˚C on the busbar. For example electrical components terminal and air temperature limits.

 

What about ARC fault containmentarc-flash

 

Under AS/NZS 3439 arc fault containment is an option to be specified, with local AS/NZS test procedures described in Annex ZD.

Under AS/NZS 61439 arc fault containment remains an optional specification with the local AS/NZS Annex ZD being included but also referencing the option of IEC TR 61641. The IEC arc fault containment test requirements are more descriptive and robust thus giving a higher level of safety.

For a more details on the AS/NZS 61439 standard please refer to: Technical News Issue #78- The evolution of Switchboard Standards

  

 

 

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