Measuring Pulse Period Duration And Operating Times; Fault Diagnosis; Insulation Fault To Earth; Insulation Fault Between The Battery Strings (Cross Fault) - Bender ISOMETER isoBAT425 Manual

Function
The image below shows the operating mode of the voltage comparators with the resul-
ting messages.
Limit
OverRange
U
510 V
Voltage fault
U
U U
Hys
Battery
voltage ok
U
U U
Hys
Voltage fault
U U U
Hys
Crossfault
U
U U
Hys
Branch open
0 V
-10 V
U
Connection
fault

3.2.5 Measuring pulse period duration and operating times

In the "sEt" menu, the measuring pulse period duration T
parameter "t ". The maximum operating times t
R and R depend on it. The modifiable measuring pulse period duration allows adjusting
F C
the ISOMETER® to the insulation behaviour of the battery.
Measuring pulse period durations which are marked with the "auto" symbol switch au-
tomatically to the longest measuring pulse period duration as long as the message "Bat-
tery voltage U is ok" is indicated. The following table shows the maximum operating
n
times t for the different alarms and measuring pulse period durations T
ae
T R R
MP F C
0.8 s 3.5 s 3.0 s
2.0 s 8.0 s 3.0 s
4.0 s 16 s 3.0 s
8.0 s 32 s 3.0 s
*
The value only applies to C oder C > 400 nF. Below this value, the absence of just one system connection is not detected.
e1 e2
**
The value only applies to R ≤ 1,5 MΩ. Above this value, the absence of just one system connection is not reliably
f
detected.
10
Comparator Status Message
can be configured with the
MP
(see page 13) of the monitoring of
ae
MP
E.01 E.02
2.1 s 6.0 s
2.1 s 6.0 s
2.1 s 15 s**
2.1 s 30 s*
Function

3.2.6 Fault diagnosis

3.2.6.1

Insulation fault to earth

The displayed value R
polarity and the amount of residual voltages U
fault location.
If the battery strings are not interconnected yet, the residual voltages U
almost identical and the nominal battery voltage U
insulation fault is only located in one string. The polarity of the residual voltages marks
the affected string. The affected battery cell can be calculated by means of the residual
voltages U or U
L+e
U = U x (1 + R
cell Lxe
If there is an additional insulation fault in the other string, determining the cell is almost
impossible, since several variables, depending on location and size of the insulation fault,
determine the residual voltages. If the battery strings are connected to form a complete
battery, the measured value "Fault location%" indicates the fault location. Clear as-
signment is only possible in the event of a single insulation fault. The value can range bet-
ween -100 % and +100 %. The sign indicates the string affected. When the fault is located
in the middle of the battery, the fault location is 0 %.
3.2.6.2

Insulation fault between the battery strings (cross fault)

The insulation fault R
strings and has no connection to earth. It can be detected via the U
measurement. If U
alarm is activated.
Depending on the fault location of the insulation fault R
same level as the voltage in a battery cell up to the maximum voltage of the series con-
nection of both battery strings can occur. R
.
tectable due to the absence of voltage. Since the coupling impedance contains a current-
limited resistance of 10 kΩ, which is connected in parallel to the series internal resistance
of 240 kΩ of the ISOMETER®, the nominal system voltage U
fault R is loaded with this resistance. For R
C
tery cell can be considered as lower limit for the fault detection. It has to be observed that
the internal resistance of the coupling impedance is only linear up to approx. 1.5 mA and
from there, limits the current to this value. In connection with the non-linear internal re-
sistance of the coupling impedance, in case of high-resistance values of R
ror/coupling error "E.02" can occur simultaneously with the overvoltage alarm.
of the ISOMETER® is the total insulation resistance R
F
and U
L+e
is about 0 V, it is very likely that the
n
.
L-e
/ R ) with ISOMETER® internal resistance R
F i
(cross fault) creates a connection between the unconnected
C
reaches or exceeds the comparator value U
n
directly at the coupling points is not de-
C
> 10kΩ, exceeding half the voltage of a bat-
C
isoBAT425_D00308_04_M_XXEN/07.2020
to earth. The
F
are an indicator of insulation
L-e
and U are
L+e L-e
= 120 kΩ
i
value of the voltage
n
, the overvoltage
CrossL
, an unloaded voltage on the
C
resulting from the insulation
n
the device er-
C