Ground Fault Check
Ungrounded Systems
The ground fault check is only necessary if the device is connected to an isolated or resonant-grounded system
and the ground fault detection is applied. The device must thus have been preset during configuration of the
device functions to Sens. Gnd Fault (address 131) not equal to Disabled. Furthermore, the direction
characteristic (S.Gnd.F.Dir.Ch, address 130) must be set to cos φ / sin φ.
If none of this is the case, this section is not relevant.
The primary check serves to find out the correct polarity of the transformer connections for the determination
of the ground fault direction.
DANGER
Energized equipment of the power system ! Capacitive coupled voltages at disconnected equipment of the
power system !
Non-observance of the following measure will result in death, severe personal injury or substantial
property damage.
²
Primary measurements must only be carried out on disconnected and grounded equipment of the
power system !
Using the primary ground fault method a most reliable test result is guaranteed. Therefore please proceed as
follows:
•
Isolate the line and ground it on both ends. During the whole testing procedure the line must be open at
the remote end.
•
Make a test connection between a single phase and ground. On overhead lines it can be connected
anywhere, however, it must be located behind the current transformers (looking from the busbar of the
feeder to be checked). Cables are grounded on the remote end (sealing end).
•
Remove the protective grounding of the line.
•
Connect a circuit breaker to the line end that is to be tested.
•
Check the direction indication (LED if allocated)
•
The faulty phase (FNo 1272 for A or 1273 for B or 1274 for C) and the direction of the line, i.e.
SensGnd
Forward
(FNo 1276) must be indicated in the ground fault protocol.
•
The active and reactive components of the ground current are also indicated (
INs Reac
, FNo. 702). The
reactive current
INs Real
, FNo. 701) is the most relevant for isolated systems. If the display shows the
message
SensGnd Reverse
(FNo. 1277), either the current or voltage transformer terminals are
swapped in the neutral path. If message
SensGnd undef.
(FNo 1278) appears, the ground current may
be too low.
•
Deenergize and ground the line.
The test is then finished.
Polarity Check for Current Input Ι
E
General
If the standard connection of the device is used with current input Ι
N
connected in the neutral point of the set
of current transformers (see also connection circuit diagram in Appendix C Connection Examples), then the
correct polarity of the ground current path usually occurs automatically.
If, however, current Ι
N
is derived from a separate summation CT (see e.g. a connection circuit diagram in the
Appendix C Connection Examples), an additional direction check with this current is necessary.
3.3.11
3.3.12
Mounting and Commissioning
3.3 Commissioning
SIPROTEC 4, 7SJ62/64, Manual 429
C53000-G1140-C207-8, Edition 08.2016
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