NESMA, the peak body for Australian switchboard manufacturers carried
out an explosive display to emphasise the importance of its safety message
regarding the consequences of not following international standards.
NESMA’s NSW Chapter tested to destruction a switchboard assembly to
demonstrate the dangerous effects of arcing at its recent seminar presentation when
it deliberately introduced excessive faults of up to 50 kA into the assembly at
the Ausgrid Testing and Certification facility in Lane Cove.
The demonstration followed an address by Norman Disney & Young
Director Rowan Peck on proposed changes to the AS/NZS 3439 series of standards
for electrical switchgear assemblies, which are in the process of being updated
to align with the new IEC parent standard series 61439 and bring local
standards more closely in line with the latest global standards.
Developed over several years, the IEC 61439 series is currently being
discussed with the industry and is proposed for adaption and incorporation into
local standards next year.
NESMA NSW Spokesman Mr Mark Betcher explains that Australasian
switchboard manufacturers are already among the world’s best in observing
safety and engineering standards. NESMA sought to demonstrate for the benefit
of all switchboard users including industrial, commercial and residential
facilities, what could go wrong when a switchboard was not manufactured to the
Key differences between the previous AS/NZS 3439 and proposed AS/NZS
61439 standards series as outlined by Mr Peck:
1. Use of more comprehensive and demanding design verifications to
replace the previous type testing concept: Every assembly to 61439 must be
verified across 13 characteristics, using a suite of options covering testing,
derivation from a tested design, or for limited conditions assessments using
design rules with built-in safety margins.
2. Restricted conditions under which switchgear devices from a verified
assembly can be substituted with alternate make or model devices.
3. Addition of a Guide for Specifiers (Part 0), which provides a summary
of the various characteristics and options for a switchgear assembly, and explains
why a choice of one over another would be made.
4. A table of items to be agreed upon between the assembly manufacturer
and the end user, which can be completed by a user or specifier to cover all of
the possible options and choices: This table enables greater consistency across
the electrical industry in selecting the requirements for a particular
5. For larger switchgear assemblies, Forms of Separation are more
clearly described through the use of example arrangements; higher Forms of Separation
(3B, 4A, 4B) now mandate the separation of external conductors from busbars for
increased safety where there is a need for certain maintenance to be carried
out on assemblies when partially live.
Mr Peck concludes that the adoption of the updated IEC 61439 series by
Australia and New Zealand will bring local practice in line with world's best
practice in electrical switchgear assembly safety and performance.