AS/NZ 3760 : 2003
The AS/NZ 3760 :
2003 is document written by Australia and New Zealand Standards that specifies the
procedures and criteria for the in-service safety inspection and testing
of electrical equipment which is designed for connection by a flexible
cord. It also applies to cord extension sets, portable outlet devices,
portable residual current devices.
This standard outlines the testing procedures for Class I
(earthed) appliances and Class II (double insulated) appliances
1. Visual Inspection
The most important
test is a Visual Inspection of the device, especially its leads. Cords
should be firmly anchored in plugs, connections made solidly with no
frayed ends. Copper terminals should be clean and not pitted.
There should be no sign of heat or melting of plugs. Leads should be
visually inspected for their entire length to ensure that there are no
cuts, cracks or breaks. This test alone represents 80% of the testing
process.
A Polarity
test is done on leads, power boards, etc, and is functional check that
Active, Neutral and especially Earth are not incorrectly wired.
This test is
important on appliances which come in contact with water such as pumps,
cleaning and cooking appliances etc, but must be performed on all
items. This will reveal if there are any hairline cracks or cuts in the
lead which will result in a low insulation resistance. The resistance
is measured at 500V or 250V with appliances with MOVs (surge
protectors) between active and neutral to earth.
No less than 1M ohm resistance should be measured form live parts to
exposed metal.
This test will
ensure that a class I appliance has a low resistance earth
connected to any external metal
No greater than 1 ohm resistance should be measured from the earthing
conductor to external metal.
5. Current Leakage
This test will test if any current is leaking out of the circuit.
Kirchhoff's current laws states that the current input is equal to the
current on the out put. in appliance terms the current flowing through
the active pin should equal to current flowing through the neutral pin.
if it does not that the current is leaking some where else. This is
normal due to a fault in the appliance.
This test must be performed on all appliances that must be energized to
be switched on. That means that a leakage test must be performed if
there is any electronic switching in the appliance (there is no way to
know if there is electronic switching in a device so it is recommended
that a leaking test is performed when possible.)
No more that 5mA in class I or 1mA in class II appliances should
be measured
6.
The Tag Itself
A tag will be
applied to the plug end of the appliance lead. It will clearly
state the date of the test or date it is due to be retested, and who
tested it or company that tested, at a minimum. But is recommend that
all these things are recorded.
Even though there
is no mention to record keeping in the standard A complete test
record should be completed. Including:
·
Asset Id
·
Test Results
·
Date Tested
·
Retest date
·
Asset Description
·
Serial Number
The
frequency of inspection is outlined in Section 2.1 of the standard. There
are recommendations in
Table 4 but
retest periods can be varied subject to a risk assessment. This
table sets out testing and inspection
intervals for various types of equipment from 3 months (for equipment
that is high use, high risk, or hire equipment) to up to 5 years (for
equipment that is not open to abuse, flexing of cords, etc).