Network Structure Description
Ring network, meshed network Greater operational zero-sequence voltages can occur in ring or meshed
networks.
The secondary operational zero-sequence voltages can be determined by
reading the residual voltage V
N sec
or the zero-sequence voltage V
0 sec
under
the symmetrical components from the device or via DIGSI.
In case you read the secondary residual voltage V
N sec
, you convert it to V
0 sec
with the Matching ratio Vph / VN parameter. You can find more
information in chapter 6.1.6 Application and Setting Notes for Measuring
Point Voltage 3-Phase (V-3ph).
If V
0 sec
is greater than 2.5 V, the value of Maximum operational V0
shall be increased to V
0 sec
⋅ 1.2.
Example:
V
N sec
= 5.000 V
Matching ratio Vph / VN = √3
V
0 sec
= 5.000 V ⋅ √3 / 3 = 2.887 V
Maximum operational V0 = 2.887 V ⋅ 1.2 = 3.464V
In most cases, the operational zero-sequence voltages are smaller than
2.500 V. Siemens recommends using the default value of 3.000 V.
Parameter: 3I0> threshold value
•
Default setting (_:13021:104) 3I0> threshold value = 0.030 A
The setting is significant only for optional trip logic for switching off permanent ground faults. Select the
setting such that the static ground-fault current exceeds the threshold value. You can disable this criterion by
setting the value to 0 A.
Parameter: Dropout delay
•
Default setting (_:13021:7) Dropout delay = 0.00 s
The parameter Dropout delay allows you to use the function also as a protection against intermittent
ground faults. With the parameter Dropout delay, the dropout of the pickup state after fault extinction is
delayed or held until the next ignition. Thus, the operate delay can go on and trip the fault.
Set the time to a value within which the new ignition can still be assigned to the previous fault. Typical values
are in a range between several hundred milliseconds and a few seconds.
Parameter: Operate delay
•
Default setting (_:13021:6) Operate delay = 0.50 s
The Operate delay parameter determines the time during which the pickup conditions must be met to
issue the operate indication. The operate indication is issued when this time expires.
The setting of the Operate delay depends on the specific application. Ensure that the pickup is delayed by
100 ms regarding the time of the ground-fault ignition.
Settings
Addr.
Parameter C Setting Options Default Setting
Trans.Gnd.flt1
_:13021:1 Trans.Gnd.flt1:Mode
•
off
•
on
•
test
off
_:13021:2 Trans.Gnd.flt1:Operate &
flt.rec. blocked
•
no
•
yes
no
6.15.5.3
Protection and Automation Functions
6.15 Sensitive Ground-Fault Detection
584 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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