Bender EDS3090, Manual

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System description
18 EDS309x_D00012_03_M_XXEN/11.2014
3.4 Operating principle for residual current measurement (
I
Δn
)
In the RCM mode the EDS309… operates based on the principle of residual current measurement. In
this case only the insulation fault locator EDS195P and a measuring clamp are used, the locating cur-
rent injector PGH18… is not required.
As per Kirchhoff's law the sum of the currents flowing into any node in a network is equal to the sum
of the currents flowing out.
Abb. 3.1: The two currents I
zu
and I
ab
have the same magnitude, however their signs are different,
such that the sum of the two currents is zero. The EDS195P detects this situation, there is no message.
Abb. 3.2: Part of the current flows through an insulation fault R
F
. The sum of the two currents
is no longer zero. As soon as the residual current reaches or exceeds the response value
there is an alarm message on the EDS195P.
In the RCM mode it is possible to measure residual currents in single and three-
phase TT or TN systems. If the system leakage capacitance ahead of the measur-
ing clamp is sufficiently high, the EDS195P can also be used for measurements in
single and three-phase IT systems. The suitability of the device is to be checked in
the specific case.
EDS195P
ISOSCAN®
I L I n
ALARM
I n
I L
INFO
MENU
HOLD
RESET
ESC
OK
I I
I
EDS195P
ISOSCAN®
I L I n
ALARM
I n
I L
INFO
MENU
HOLD
RESET
ESC
OK
I
I
I