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2. Technical and
General Question Corner
Q. Why does AS/NZS 3000:2000 require 0.5 Ohms on earth
continuity testing while AS/NZS 3760:2001 requires 1 Ohm?
A. AS/NZS 3000:2000 is the Standard that
relates to electrical installations while AS/NZS 3760 2001 covers
the in service safety inspection and testing of electrical
equipment. As such it has been determined in both Australia and
New Zealand that the resistance values for earth continuity under
each of the Standards in question will be different.
The reason for the difference is that each Standard has been
developed from a different perspective to accommodate differing
electrical needs.
One of the objectives of AS/NZS 3000:2000 is to achieve
minimum resistance between the MEN point of any electrical
installation and the mass of earth in the event of a fault.
It is considered that the 0.5 Ohms stated in AS/NZS 3000:2000
is a reasonable level to achieve the desired objective.
AS/NZS 3760:2001 covers a wide range of electrical equipment
that can be being entered into service for the first time, in
service, have been in service or is available for hire or resale.
This equipment includes appliances.
The range of equipment covered by AS/NZS 3760:2001 can also
have varying lengths and types of flexible cords as a means of
electrical supply.
One of the objectives of AS/NZS 3760:2001 is to achieve, in
the event of a fault, a reasonably good earth path from any piece
of electrical equipment to the point where the initial earthing
of the equipment is obtained. That point in many cases is a
general purpose socket outlet.
It is considered that the 1 Ohm stated in AS/NZS 3760:2001
achieves the desired objective whilst taking into account the
wide range of equipment involved.
Q. Can a line mechanic carry out work in relation to
street lights?
A. Regulation 19 of the Electricity
Regulations 1997 states, in part, that line mechanics may do
prescribed electrical work that involves the construction and
maintenance of electric lines.
An electric line means all conductors (including fittings
supporting, or connected to, those conductors), whether above or
below ground, that are used, or intended to be used, in, or in
connection with, the supply of electricity from the outgoing
terminals of a generating station, a building enclosure, or other
structure to -
(a) the incoming terminals of another building, enclosure or
other structure; or
(b) an electrical appliance, in any case where the electrical
appliance is supplied with electricity other than from a terminal
in a building, enclosure, or other structure.
An electrical appliance means any appliance that uses, or is
designed or intended to use, any other form of energy.
It follows therefore that a street light forms part of an
electric line and as such a registered line mechanic
(distribution) is entitled, by virtue of regulation 19, to carry
out prescribed electrical work associated with the installation
and maintenance of street lighting.
Q. Does NZS 5261:2003 impact on electrical equipment?
A. Section 2.7.1.6 of NZS 5261:2003, which
relates to the installation of LPG cook tops states that where a
cylinder is located inside, the cylinder shall not be in the same
compartment as a power point or electrical appliance, for example
a waste disposal unit or a dishwasher.
Q. Please clarify the partnership between the
Electrical Workers Licensing Group and Inland Revenue? I am
concerned about the release of my personal information.
A. The Board is the statutory body that has
the authority to hold personal information. Such information is
subject to privacy and official information legislation and
numerous requests are made each year by various organisations or
persons for the release of documents under the Official
Information Act. In all cases when information is requested about
an individual, where that information has not been in the public
domain, that individual is informed that a request has been made
and the individual is given the opportunity to state whether or
not the requested information should be released.
As the partnership with Inland Revenue is one where printed
information received from Inland Revenue is made available to the
electrical/electronic industry the release of personal
information is entirely separate.
The release of personal information provisions apply
irrespective of whether or not the partnership with Inland
Revenue exists.
Q. Is it necessary to drive an earth electrode for the
MEN connection provided at a metal lighting pole when the pole is
set approximately two metres into the ground with the light being
supplied from the local distribution system?
A. An additional driven earth electrode is
not required provided the pole itself provides a connection with
earth which is equivalent to or better than that of an earth
electrode.
There should be a proper means of making the MEN connection
within the pole by the provision of a stud or other suitable
means.
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