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TGH1266E - 05/04
Operating Principle of the EDS3065
I∆=0
PE
I
ab
I
zu
I∆=0
PE
I
ab
I
zu
R
F
Operation in the
RCM-Mode
In the RCM mode, the EDS3065 operates according to the principle of residual current
measurement. In this case, only the EDS165 evaluator unit with the clamp-on probe is used, and
the PGH185 test device is not required.
In accordance with Kirchhoff’s Law, the sum of the inflowing currents at every intersection in a
network is equal to the sum of the outflowing currents.
The two currents I
to
and I
from
are equal in
quantity but have different directions, so
that the resultant sum is zero. The EDS165
recognises this and no message is generated.
A portion of the current is flowing away
via an insulation fault R
F
. The sum of the
currents is no longer zero. If the residual
current is equal to or greater than the
response value, the EDS165 will generate
a message.
In the RCM mode, residual currents can be measured in one- and three-phrase TT or TN systems.
If the system leakage capacitance upstream of the clamp-on probe is sufficiently high, the EDS165
can also be used for measurements in one- and three-phase IT systems. Its suitability for this
purpose must be checked in each individual case.
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