Important information
17
isoHV425_D00082_03_M_XXEN/05.2020
3.2.5
Measuring and response times
The measuring time is the time required to detect a measured value. The measuring
time is reflected in the operating time
t
ae
. The measuring time for the measured insula-
tion resistance value is mainly determined by the required measuring pulse duration,
which depends on the insulation resistance
R
F
and the system leakage capacitance
C
e
of the system to be monitored. The measuring pulse is produced by the measuring
pulse generator 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 independent and con-
siderably shorter.
Total response time
t
an
The total response time
t
an
is the sum of the operating time t
ae
and the response delay
time
t
on
.
Operating time
t
ae
The operating time
t
ae
is the time required by the ISOMETER® to determine the meas-
ured value. For the measured insulation resistance value, it depends on the insulation
resistance
R
F
and the system leakage capacitance
C
e
.
Response delay
t
on
The response delay
t
on
is set uniformly for all messages in the "t" menu using the param-
eter "ton", whereby each alarm message specified in the signalling assignment has its
own timer for
t
on
. This delay time can be used for interference suppression in the case
of short measuring times.
An alarm will only be signalled when a threshold value of the respective measured val-
ue is violated for the period of
t
on
without interruption. Every time the threshold value
is violated within the time
t
on
, the response delay "ton" restarts once again.
Delay on release
t
off
The delay on release
t
off
can be set uniformly for all messages in the "t" menu using the
parameter "toff", whereby each alarm message listed in the signalling assignment hast
its own timer for
t
off
. An alarm will continuously be signalled until the threshold value
of the respective measured value is not violated (including hysteresis) for the period of
t
off
without interruption. Each time the threshold value is not violated for the period of
t
off
, the delay on release "toff" restarts.
Start-up delay
t
After connection to the supply voltage
U
s
the alarm indication is supressed for the pre-
set time (0…10 s) specified for parameter "t".
