Polarity Check For Current Input Ι - Siemens 7SC80 Manual

Mounting and Commissioning
3.3 Commissioning
!
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.
Primary measurements must only be carried out on disconnected and grounded equipment of the
²
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 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 (
reactive current
message SensGnd Reverse (FNo. 1277), either the current or voltage transformer terminals are
swapped in the neutral path. If message
be too low.
•
Deenergize and ground the line.
The test is then finished.
3.3.13 Polarity Check for Current Input Ι
General
If the standard connection of the device is used with current input Ι
of current transformers (see also connection circuit diagram in Appendix
correct polarity of the ground current path usually occurs automatically.
If, however, current Ι
Appendix C Connection
If the device features the sensitive current input for Ι
system, the polarity check for Ι
section. Then this section is not relevant.
Otherwise the test is done with a disconnected trip circuit and primary load current. It must be noted that
during all simulations that do not exactly correspond with situations that may occur in practice, the non-
symmetry of measured values may cause the measured value monitoring to pick up. This must therefore be
ignored during such tests.
492
INs Real , FNo. 701) is the most relevant for isolated systems. If the display shows the
SensGnd undef. (FNo 1278) appears, the ground current may
N
is derived from a separate summation CT (see e.g. a connection circuit diagram in the
N
Examples), an additional direction check with this current is necessary.
was already carried out with the ground fault check according to the previous
N
connected in the neutral point of the set
N
C Connection
and if it is used in an isolated or resonant-grounded
N
SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017
INs Reac , FNo. 702). The
Examples), then the