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Mounting and Commissioning
3.3 Commissioning
• 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.
3.3.12
Polarity Check for Current Input I
General
If the standard connection of the device is used with current input I
current transformers (see also connection circuit diagram in Appendix A.3), then the correct polarity of the
ground current path usually occurs automatically.
If, however, current I
Appendix A.3), an additional direction check with this current is necessary.
If the device features the sensitive current input for I
system, the polarity check for I
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.
DANGER!
Hazardous voltages during interruptions in secondary circuits of current transformers
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.
Directional Testing for Grounded Systems
The check can either be carried out with function „directional ground fault protection" (address 116) or with the
function „ground fault detection" (address 131), which can be operated 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 (see Figure 3-29). If no connection on the e–n windings of the voltage transformer is provided, the
corresponding phase is disconnected on the secondary side (see Figure 3-30). Only the current of the trans-
former which is not provided with voltage in its voltage path is fed into the current path. If the line carries resis-
tive-inductive load, the protection is subject to the same conditions as exist during a ground fault in line direc-
tion.
The directional ground fault protection must be configured to enabled and activated (address 116 or 131). Its
pickup threshold must be below the load current of the line; if necessary the pickup threshold must be reduced.
The parameters that have been changed, must be noted.
342
is derived from a separate summation CT (see e.g. a connection circuit diagram in the
N
was already carried out with the ground fault check according to the previous
N
N
connected in the neutral point of the set of
N
and if it is used in an isolated or resonant-grounded
N
E50417-G1140-C344-A5, Release date 11.2012
SIPROTEC, 7SK80, Manual
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