Checklist for Insulation Tests
Page 15
3
Earthing
In general, a safe and reliable test is only possible with proper earthing. An
incorrect or faulty earth can, under certain circumstances, result in electrisa-
tion of the tester. This can be ruled out with proper use and earthing of the
tester.
3.1
Methods of Earthing
The conductive connection between the object to be tested and the Isotest can
be created in various ways.
3.1.1 Direct connection (earthing) between test objective and Isotest
With this method of earthing, the earthing cable supplied (15 m) is connected
to the tester via the earthing plug (see section 1.2). The earthing clip at the
other end of the earthing cable is now attached to a conductive part of the test
specimen. Ensure that the point to which the earthing clip is fastened is
metallically bare in order to ensure a reliable connection
3.1.2 Indirect earthing with the earthing rod and trailing earth
With this method of earthing, the test specimen is connected to the ground at
an accessible and metallically bare point using the earthing rod. (Push the
earthing rod as far into the ground as possible.) Connect the earthing clip to a
metallically bare part of the test specimen (pipe, tank, etc.). Ensure that the
section to be tested and the earthing point are electrically conductive, i.e. are
not connected e.g. via insulators. The connection between the ground and the
insulation tester is effected via the trailing earth, whereby the earthing plug of
the trailing earth is connected to the earthing socket of the Isotest.
As, from experience, we know that problems are frequently encountered with
the indirect earthing method, the following table contains a list of the possible
faults and their remedies:
