Direction Test of Ground Quantities for Directional Ground-Fault
Functions
Overview
If the CT and VT connections are in the way that the ground quantities (3I0 and V0) are calculated by the
device from the phase quantities, then, no additional directional test is required. Testing according to
11.2 Direction Test of the Phase Quantities (Current and Voltage Connection) is sufficient.
If the ground current IN or the ground voltage VN is directly measured via a device input (usually I4 or V4), the
correct polarity of the ground current and the ground voltage path must be checked.
DANGER
Live system parts! Capacitive coupled voltages on dead parts!
Noncompliance with the following measures can lead to death, serious physical injury, or consider-
able material damage.
²
Primary measures may be performed only on dead and grounded system parts.
Directional Testing for Solid or Resistive-Grounded Systems
Primary Test
The primary test is used for the evaluation of the correct polarity of the transformer connections for the deter-
mination of the ground-fault direction.
To generate a zero-sequence voltage V0, the e-n winding of one phase in the voltage-transformer set (for
example, phase A) is bypassed, see Figure 11-1. If no connection on the e–n windings of the voltage trans-
former is provided, the corresponding phase is disconnected on the secondary side, see Figure 11-2. Only the
current of the transformer in the phase of which the voltage is missing is transferred via the current circuit. If
the line carries resistive-inductive load, the protection is subject to the same conditions as existing during a
ground fault in line direction.
For directional testing, the Directional ground-fault protection function (67N) is configured and at least one
stage is switched on. The pickup threshold of the stage must be below the load current of the line. If not, the
binary input signal
(_:2311:501) >Test of direction
can be activated to lower the threshold tempo-
rarily for testing means without changing the respective parameter.
After switching the line on and off again, you can check the pickup signal of the directional protection stage in
the fault log. A forward information must be logged. If no pickup information is logged at all, the 3I0 or U0
threshold is not exceeded.
If a wrong direction is logged, one of the following conditions may have occurred:
•
The direction of the load flow is from the line towards the busbar.
•
The ground-current connection is incorrect.
•
The voltage connection is incorrect.
NOTE
Siemens recommends not to change parameter settings for the test. However, if parameters were changed
for this test, they must be returned to their original state after completing the test!
11.3
11.3.1
11.3.2
Functional Tests
11.3 Direction Test of Ground Quantities for Directional Ground-Fault Functions
1374 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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