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TGH1266E - 05/04
Points to be Considered before Use
Limits of Insulation
Fault Location
All the characteristic curves on the foregoing pages are valid for a maximum test current of 25 mA.
If the test current has been limited to 10 mA, the DC axis of the test current limitation in
characteristic curve 4 is shifted accordingly to this value of 10 mA.
Limitation of the test current to 10 mA is particularly intended for the use of the EDS3065 in DC
control systems with consumers which may already operate at very low currents. If the test current
limitation is activated in AC systems, the maximum test current is then reduced to factor 0.5 in AC
systems or 0.67 in 3AC systems respectively. Of course, these factors are valid for a maximum test
current of 25 mA as well (see characteristic curve 4).
It is a well-known fact that everything in this world has its limits. This principle even applies to
the measurement technology of the EDS3065. Modern supply systems nowadays contain a large
number of components which may give rise to influences and faults.
Here are some examples of faults from the viewpoint of the EDS3065:
• system leakage capacitances
• excessively high leakage currents
• transient leakage currents
• low-frequency leakage currents
The limit conditions are cited in this operating manual. However, because of the large number of
possibilities, we cannot make definitive statements about every type of fault compatibility, nor
about functional limits. In case of doubt, you must clarify the suitability of the EDS3065 for the
application in question by consulting a BENDER adviser.
The conditions, and the reactions of the EDS3065 if the conditions are exceeded, should be
explained at this point:
• response sensitivity: for this purpose, curve 3 in this chapter should be taken into
account.
• influence of system leakage capacitances: curves 2a and 2b in this chapter show the
response sensitivity in relation to the leakage capacitance of the total system. If the
leakage capacitance exceeds the permissible value at one junction downstream of the
clamp-on probe, incorrect messages may appear on the EDS165 evaluator.
• maximum leakage currents: the maximum permissible system-related leakage current
under which the evaluation will still function properly is limited to 10 A. If the leakage
current exceeds 10 A, discriminating fault detection can no longer be undertaken.
Leakage currents > 10 A are shown by the indication {I
∆
> 10 A} in the display of the
EDS165.
• transient leakage currents: switching and adjusting activities in the system may generate
transient leakage currents which influence the evaluation of the test signal. These
transient leakage currents can only be filtered out to a certain extent. It cannot be ruled
out that periodic disturbances which happen to have the same periodic duration,
amplitude and signal frequency as the internal signal scanning may result in faulty
measurements and may therefore lead to actuating errors.
However, the probability of this happening is extremely low. It is not possible to give a
precise definition of these limit conditions because they depend on the nature of the
system.
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