Siemens 7SJ82, Manual

Page: 1009 / 1638

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 setting
(_: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 7-2 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
Secondary setting value: 0.75 ⋅ 0.071 A = 0.053 A
i
i
NOTE
Use senstive device current inputs in order to apply secondary thresholds of < 30 mA.
Resetting the Counters via Protocols IEC 60870-5-103, IEC 60870-5-104, DNP3, or Modbus
The following example shows how to use a function chart (CFC) to reset the counters with the protocols
IEC 60870-5-103, IEC 60870-5-104, DNP3, or Modbus.
Capacitor Bank Protection
7.5 Current-Unbalance Protection for Capacitors, 1-Phase
SIPROTEC 5, Overcurrent Protection, Manual 1009
C53000-G5040-C017-8, Edition 07.2017