www.megger.com
PAT400 Series
78
Test button failure
The RCD test sequences include an RCD test button check. This works by automatically monitoring the 230 V supply through the RCD.
If the RCD test button fails to trip the RCD the RCD has failed. However the PAT400 will wait for a trip. In this case a manual fail is
required. PRESS THE “ F ” key. This will log the test as a fail and allow the result to be saved.
A.6 Power lead/extension lead testing
Power cords and extension leads are tested in a similar way. The principle differences are the need to use an extension lead adaptor when
testing extension leads, as the lead must be looped back to the PAT400 to allow bond and polarity testing.
Extension leads or power leads with surge protection should be tested with an Insulation test voltage of 250 V. This prevents the surge
protection from operating and artificially failing the lead.
Extension leads fitted with RCDs should be tested as per an ordinary plug-in RCD. In addition the following tests can be used:
Bond test (continuity test)
Differential leakage test (The RCD must be switched on manually during the test).
The Insulation test will not test beyond the RCD and consequently has little value.
Lead length up to 50m can be compensated. However they can exceed the recommended length for their cross section.
Maximum recommended length for extension leads:
CSA of cores (mm2)
Maximum length (m)
1.25
12
1.5
15
2.5
25
Any lead longer than the recommended length should be fitted with a Residual Current Device (RCD) with a rated operating current not
exceeding 30mA, as the earth resistance can be high enough that the operation of standard protective devices cannot be guaranteed.
A.7
Flash testing (PAT450 only)
Flash testing measures the leakage current when high test voltages are applied to an asset.
Flash testing is NOT recommended for portable appliance testing as it is a destructive test. Repeated use on an asset can cause premature
failure or possible electrical damage.
A.8
Parallel Earth Path WARNING:
Occasionally there may be a parallel earth path between the asset under test and the system earth. This can arise from a Class I asset
touching other earthed metal equipment, or being electrically in contact with the floor. This can create a resistance path back to the
electrical supply earth that is in parallel with the asset’s own earth return. Under these circumstances the PAT400 will warn the operator
by displaying the message:
