Application And Setting Notes (Advanced Stage) - Siemens 6MD85 Manual

Protection and Automation Functions
7.5 Overcurrent Protection, Ground
7.5.8.2

Application and Setting Notes (Advanced Stage)

Binary Input Signal: Dynamic settings
•
Default setting (_:751:26) Dynamic settings = no
Parameter Value
no
yes
Influence of AREC
The example of how the overcurrent-protection stage (1st stage) can be used as a fast stage before automatic
reclosing describes the influence exerted by AREC.
The setting of the overcurrent level (1st level) results from the time-grading schedule. It is to be used as fast
stage before an automatic reclosing. Because fast disconnection of the short-circuit current takes priority over
the selectivity prior to reclosing, the Operate delay parameter can be set to 0 or to a very low value. To
achieve the selectivity, the final disconnection must be done with the grading time.
AREC is set to 2 reclosings. A secondary Threshold of 1.5 A and a Operate delay of 600 ms are
assumed (according to the time-grading schedule) for the overcurrent-protection stage. The standard settings
of the stage are set to these values.
To realize the application, the configuration settings Effected by AR cycle 1 and Effected by AR
cycle 2 are changed in the example to yes (= influenced). This activates the AR cycle 1 and AR cycle
2 input signals within the stage. When they become active, they switch to the assigned dynamic settings.
The two dynamic settings Operate delay assigned to these input signals (sources of influence) are set to
the time delay 0 (instantaneous tripping). The two dynamic settings Threshold assigned to these input
signals are set to the normal threshold value of 1.5 A.
If the threshold value (1.5 A) is exceeded before AREC 1 and AREC 2, the overcurrent-protection stage trips
instantaneously. If the fault still exists after AREC 2 (unsuccessful AREC), the stage trips with the time delay of
600 ms according to the time-grading schedule.
Influence of External Devices
The influence of an external device can also be configured. The above is an example of how the overcurrent-
protection stage (1st stage) can be used as a fast stage before automatic reclosing, in which case the AREC
function is performed by an external device.
To realize the application, the configuration setting Effected by binary input must be changed to yes
(= influenced). This activates the >Activ. dyn. settings input signal within the stage. When the input
signal becomes active, it switches to the assigned dynamic settings. The external device must provide the
Cycle 1 and Cycle 2 signals or, alternatively, an AREC ready signal. The signals must be connected with
the binary input signal >Activ. dyn. settings.
The dynamic setting Operate delay, which is assigned to the input signal (source of influence) >Activ.
dyn. settings, is set to the time delay 0 (instantaneous tripping). The dynamic setting Threshold
assigned to this input signal is set to the normal threshold value of 1.5 A.
If the threshold value (1.5 A) is exceeded before AREC 1 and AREC 2, the overcurrent-protection stage trips
instantaneously. If the fault still exists after AREC 2 (unsuccessful AREC), the stage trips with the time delay of
600 ms according to the time-grading schedule.
666
Description
The influence on the overcurrent-protection stage by device-internal or
external functions is not necessary.
If a device-internal function (automatic reclosing function or cold-load
pickup detection) or an external function should affect the overcurrent-
protection stage (such as change the setting of the threshold value or time
delay, blocking of the stage), the setting must be changed to yes.
This makes the configuration parameters Influence of function...
as well as the dynamic settings Threshold, Operate delay and Stage
blocked of the stage visible and enables the settings to be set for the
specific influence.
SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017