Polarity Check For Current Input I - Siemens siprotec SJ62 User Manual

3.3.12 Polarity Check for Current Input I

General
Directional Testing
for Grounded
Systems
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
• 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 rele-
vant for isolated systems. If the display shows the message „SensGnd Reverse"
(FNo. 1277), either the current or voltage transformer terminals are swopped 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.
If the standard connection of the device is used whereby current input I
in the starpoint of the set of current transformers (refer also to the connection circuit
diagram in the Appendix A.3), then the correct polarity of the ground current path in
general automatically results.
If, however, current I is derived from a separate summation CT (see e.g. a connection
N
circuit diagram in the Appendix A.3), an additional direction check with this current is
necessary.
If the device is provided with the sensitive current input I
isolated or resonant-grounded system, the polarity check for I
out with the ground fault check according to the previous section. Then this section
can be ignored.
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 mea-
sured value monitoring to pick up. This must therefore be ignored during such tests.
DANGER!
Hazardous voltages during interruptions in secondary circuits of current trans-
formers
Non-observance of the following measure will result in death, severe personal injury
or substantial property damage.
Short-circuit the current transformer secondary circuits before current connections to
the device are opened.
The check can either be carried out with function „directional ground fault protection"
(address 116) or function „ground fault detection" (address 131), which can be oper-
ated as additional fault protection.
In the following the check is described using the „directional ground fault protection"
function (address 116) as an example.
To generate a displacement voltage, the e–n winding of one phase in the voltage
transformer set (e.g. A) is bypassed (refer to Figure 3-38). If no connection on the e–
N
3.3 Commissioning
is connected
N
and it is connected to an
N
was already carried
N
434