Bender ISOMETER isoBAT425, Manual

Page: 9 / 35

Function Function
isoBAT425_D00308_04_M_XXEN/07.2020
9
In addition, the coupling impedance contains two capacitances for a necessary minimum
leakage capacitance to earth.
3.2.2 Measured values
The following parameters are measured by means of the ISOMETER®:
The measured value ranges and the resolution are indicated in the following table:
Parameter Description Unit
R
F
Insulation resistance to earth
kΩ
U
n
Nominal system voltage between L+ and L-
V
DC
U
L+e
Residual voltage between L+ and earth
V
DC
U
L-e
Residual voltage between L- and earth
V
DC
Faulty conduc-
tor
Distribution of the insulation resistance R
F
between ter-
minals "L+" and "L-".
In the LC display, the fault location is marked with a plus
or a minus sign preceding the value
R
F
.
%
Value Interface Value range Resolution
R
LCD
1 kΩ 999 kΩ 1 kΩ
1.0 MΩ 10.0 MΩ 0.1 MΩ
BMS
1 kΩ 20000 kΩ 1 kΩ
Modbus, IsoData 1 kΩ 20000 kΩ 1 kΩ
U
LCD
0 V ±99.9 V 0.1 V
±100 V ±500 V 1 V
BMS
0 V 500 V 1 V
Modbus, IsoData
0 V ±500 V 0.1 V
C
LCD
0 nF 999 nF 1 nF
1.00
μ
F 9.99
μ
F 0.01
μ
F
BMS
0 nF 9990 nF 1 nF
Modbus, IsoData
0 nF 9990 nF 1 nF
3.2.3 Monitoring of the insulation resistance and the system leakage
capacitance
The insulation resistance R
F
as well as the system leakage capacitance C
e
to earth are me-
asured. The results are the total values from the sub-components R
F1
|| R
F2
as well as
C
e1
+ C
e2
. The system leakage capacitance value C
e
is only updated above R
F
= 10 kΩ.
When the insulation resistance R
F
reaches or falls below the threshold values R1
(prealarm) or R2 (main alarm), an alarm message is issued. Parameters R1 and R2 can be
found in the response value menu "AL" (see table on
page 19 ). If by means of the measu-
red voltages the faulty conductor can be assigned to the plus or the minus string, only the
corresponding "L+" or "L-" alarm will be issued. Otherwise, both alarms are issued to-
gether.
The system leakage capacitance C
e
is monitored on its compliance with the maximum
permissible value for the ISOMETER®. If the measured value of the system leakage
capacitance
C
e
exceeds 4 μF, the device error "E.07" with the alarm message "Device er-
ror" is issued.
The measurement method requires a low-resistance connection between terminals
"
L+
"
and
"
L-
"
. If the battery strings are still separated from each other, the connection will be
established via the coupling impedance. The 12 kΩ internal resistance of the coupling im-
pedance is included in the measured value
R
F
. If R
F
is below 100 kΩ, a measured value de-
viation of approx. +2 kΩ must be expected. If the battery strings are connected to form a
complete battery, the internal resistance of the battery establishes the low-resistance
connection and the deviation due to the coupling impedance is omitted.
3.2.4 Undervoltage/overvoltage monitoring
The nominal system voltage value U
n
is 400 V. With an overvoltage of 25 %, a maximum
of 500 V are permissible. The nominal system voltage U
n
is measured in V
DC
and V
RMS
. The
root-mean-square value is a true RMS value and is only required for overload detection
(over range) of the system coupling. In addition, the residual voltages
U
L+e
as well as
U
L-e
to earth are determined. The voltage values on the LC display and the interface are
averaged to improve the resolution and are time-delayed. The comparators of the system
voltage monitoring use the non-delayed, non-averaged system voltage. Therefore, minor
deviations between the response of the voltage monitoring and the indicated voltage
value are possible.
The parameters (U1 <, U1 >, U2 < and U2 >) for monitoring the nominal system voltage
U
n
can be set in the response value menu "AL" (see page 19 ). The maximum undervoltage
value is limited by the overvoltage value. If the nominal system voltage U
n
reaches, falls
below or exceeds the limit values (U < or U >), an alarm will be signalled. The alarm will
be deleted when the threshold values plus hysteresis (see
page 19 ) are no longer vio-
lated.