Function
20
isoMIL425_D00203_03_M_XXEN/03.2019
L2/-. If an assignment is not possible, for example in the event of a symmetri-
cal insulation fault, the message corresponding to "+" and "- " are shown to-
gether.
The message "test" indicates a self test.
The message "S.AL" indicates a so-called "device start with alarm". After con-
necting to the supply voltage
U
s
and setting the parameter value to
"S.AL = on", the ISOMETER® starts with the insulation measurement value
R
F
= 0 Ω and
Z
F
= 0 Ω in Z mode and displays all activated alarms. The alarms
will be cleared only when the measured values are up-to-date and no
thresholds are exceeded. In the factory setting "S.AL = off", the ISOMETER®
starts without an alarm.
It is recommended that the value set for the parameter "S.AL" is identical for
both relays.
3.2.7
Measuring and response times
The measuring time is the period essential for the detection of the measuring
value. The measuring time is reflected in the operating time
t
ae
.
In R mode, the measuring time for the insulation resistance value is mainly de-
termined by the required measuring pulse duration, which depends on the in-
sulation resistance
R
F
and system leakage capacitance
C
e
of the system to be
monitored. The measuring pulse is produced by the measuring pulse genera-
tor integrated in the ISOMETER® . The measuring times for
C
e
,
U
L1e
,
U
L2e
and
R
% are synchronous. System disturbances may lead to extended measuring
times. In contrast, the time for the system voltage measurement
U
n
is inde-
pendent and considerably shorter.
In Z mode a fixed and short measuring pulse time is applied, leading to a short
measuring time for all measured values.
Total response time
t
an
The total response time
t
an
is the sum of the operating time
t
ae
and the
on-delay time
t
on
.
