Direction Check With Load Current - Siemens SIPROTEC 7SK80 Manual

3.3.9

Direction Check with Load Current

Preliminary Remark
Note
The direction check is only relevant for devices with voltage transformers.
≥ 10 % of Load Current
The correct connection of the current and voltage transformers is tested via the protected line using the load
current. For this purpose, connect the line. The load current the line carries must be at least 0.1 · I
current should be in-phase or lagging the voltage (resistive or resistive-inductive load). The direction of the load
current must be known. If there is any doubt, network or ring loops should be opened. The line remains ener-
gized during the test.
The direction can be derived directly from the operational measured values. Initially the correlation of the mea-
sured load direction with the actual direction of load flow is checked. In this case the normal situation is
assumed whereby the forward direction (measuring direction) extends from the busbar towards the line
P positive, if active power flows into the line,
P negative, if active power flows towards the busbar,
Q positive, if reactive power flows into the line,
Q negative, if reactive power flows toward the busbar.
Figure 3-28
All signs of powers may be inverted deliberately. Check whether polarity is inverted in address 1108 P,Q sign
in the P.System Data 2. In that case the signs for active and reactive power are inverse as well.
The power measurement provides an initial indication as to whether the measured values have the correct po-
larity. If both the active power and the reactive power have the wrong sign and 1108 P,Q sign is set to not
reversed, the polarity according to address 201 CT Starpoint must be checked and corrected.
The line is switched off again after completion.
Note
Reset the pickup values changed for the check to valid values.
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A4, Release date 08.2010
Apparent Load Power
Mounting and Commissioning
3.3 Commissioning
. The load
Nom
325