Bender ISOMETER isoRW425 User Manual

Function
15
isoRW425_D00052_03_M_XXEN / 02.2017
3.2 Functional description
The ISOMETER® measures the insulation resistance R
F
and the leakage capac-
itance C
e
between the system to be monitored (L1/+, L2/-) and earth (PE).
Z mode (selectable in the "SEt" menu) calculates the insulation impedance Z
F
from R
F
and C
e
with a system frequency parameter f
n
= 50 Hz or f
n
= 60 Hz. The
r.m.s. value of the mains voltage U
n
between L1/+ and L2/-, as well as the DC
voltages between L1/+ and earth (U
L1e
) and between L2/- and earth (U
L2e
) are
also measured.
From a minimum value of the DC system voltage, the ISOMETER® determines
the fault location in % (represented by "R %"), which shows the distribution of
the insulation resistance between conductors L1/+ and L2/-. The distribution
is indicated by a positive or negative sign preceding the insulation resistance
measurement. The value range of the fault location is ±100 %:
The partial resistances can be calculated from the total insulation resistance R
F
and the fault location (R %) using the following formula:
Also from a minimum value of the DC system voltage, the ISOMETER® deter-
mines the insulation resistance R
UGF
from the DC voltages U
L1e
and U
L2e
. It is
an approximate value for one-sided insulation faults and can be used as a
trend indicator in cases where the ISOMETER® has to adapt to an R
F
and C
e
relation that varies considerably.
It is possible to assign the detected fault or the faulty conductor to an alarm
relay via the menu. If the values R
F
, Z
F
or U
n
exceed the response values acti-
vated in the "AL" menu, this will be indicated by the LEDs and relays K1 and K2
according to the alarm assignment set in the "out" menu. In addition, the op-
eration of the relay (n.o. / n.c.) can be set and the fault memory "M" activated.
Display Meaning
–100 % one-sided fault at conductor L2/-
0 % symmetrical fault
+100 % one-sided fault at conductor L1/+
Fault at conductor L1/+
R
L1F
= (200 % * R
F
)/(100 % – R %)
Fault at conductor L2/-
R
L2F
= (200 % * R
F
)/(100 % + R %)

Bender ISOMETER isoRW425 Specifications

General

Brand	Bender
Model	ISOMETER isoRW425
Category	Measuring Instruments
Language	English