NESMA’s explosive switchboard display demonstrates importance of international standards

Australian switchboard manufacturers’ peak body NESMA demonstrated the
explosive effects of arcing to underline the importance of ensuring
international standards in switchboard assemblies.

NESMA’s NSW Chapter delivered this important safety message at a recent seminar
presentation when it deliberately introduced excessive faults of up to 50 kA into
the switchboard 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 world 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.

According to NESMA NSW Spokesman Mr Mark Betcher, Australasian
switchboard manufacturers are already leading the world in observing safety and
engineering standards. The demonstration aimed to convey to switchboard users in
industrial, commercial and residential facilities, about what could go wrong
when a switchboard was not manufactured to the relevant standards.

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
application.

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 align local practice with world’s best practice
in electrical switchgear assembly safety and performance.

Mr Betcher thanked Mr Peck and the sponsors who made the event possible,
including Schneider Electric, IPD Industrial Products and Austral Wright
Metals.