Siemens 7SJ82, Manual

Page: 985 / 1638

If no counter stages are applied, Siemens recommends switching the automatic compensation off and using
the manual compensation. You can find more information on this recommendation in chapter
7.4.4.2 Appli-
cation and Setting Notes (setting notes for the operate delay of the I> stage).
If the counter stages are applied, the automatic compensation must be switched on, otherwise the counting
function will not work.
Parameter:
De-energ.time w/o comp.
•
Default setting
(_:2311:104) De-energ.time w/o comp.
=
2.00 s
In case of networks faults, the faulty phases are discharged. With the returning voltage after fault clearance,
charging takes place. For such conditions, Siemens recommends that no automatic full compensation takes
place in the affected phases. Otherwise, C-element defects occurring in this period (for example, because of
discharging stress due to network-fault inception) will not be detected.
With the parameter
De-energ.time w/o comp.
, you define the duration of short de-energization after
which no automatic compensation takes place. The parameter must be set to a value larger than the slowest
fault-clearing time in your network plus a safety margin.
If the setting is set to 0 s, an automatic full compensation is carried out after each energizing detection.
Parameter:
Normalization with Ic
•
Default setting
(_:2311:100) Normalization with Ic
=
no
This parameter applies equally to all stages of the function.
Parameter Value Description
no
Select this setting if you can safely assume that I
c
will not change for opera-
tional reasons or if you do not desire normalization of the unbalanced
current with I
c
.
Please consider that the protection sensitivity will decrease with decreasing
I
c
.
yes
Select this setting if you want to keep the sensitivity of the protection
stages constant during changes of I
c
.
Parameter:
Thresh. defective C-elem.
•
Default
(_:2311:102) Thresh. defective C-elem.
=
0.030 A
Set the parameter
Thresh. defective C-elem.
to ensure that the jump in the unbalanced current
caused by the faulty C-element is detected. Information about occurring unbalanced current as a consequence
of single faulty C-elements will be provided by the manufacturer of the capacitor bank. Siemens recommends
to set the threshold value to approx. 75 % of the unbalanced current that occurs after the fault of the 1st C-
element.
Example 1: Information about the Unbalanced Current Available from the Manufacturer of the Capacitor Bank
Table 7-1 Unbalanced Current, Depending on the Number of Faulty C-Elements
Number of Faulty C-Elements Primary Unbalanced Current
0 0.00 A
1 0.71 A
2 1.47 A
3 2.29 A
... ...
Assumed current transformer ratio: 10 A/1 A
Primary unbalanced current if 1st C-element fails: 0.71 A
Secondary unbalanced current if 1st C-element fails: 0.071 A
Capacitor Bank Protection
7.4 Current-Unbalance Protection for Capacitors, 3-Phase
SIPROTEC 5, Overcurrent Protection, Manual 985
C53000-G5040-C017-8, Edition 07.2017