Figure. 5.2.2 - 73. Relay behavior when voltage injected during an earth fault.
Troubleshooting
When the measured voltage values differ from the expected voltage values, the following table offers
possible solutions for the problems.
Problem
Check / Resolution
The measured
voltage amplitude in all
phases does not match
the injected voltage.
The scaling settings or the voltage measurement mode may be wrong, check that the settings
match with the connected voltage transformer (
Measurement
→
Transformers
→
VT Module).
The measured
voltage amplitude does
not match one of the
measured phases./
The calculated U0 is
measured even though it
should not.
Check the wiring connections between the injection device or the VTs and the relay.
The measured
voltage amplitudes are OK
but the angles are
strange./
The voltage unbalance
protection trips
immediately after
activation./
The earth fault protection
trips immediately after it is
activated and voltage
calculated.
The voltages are connected to the measurement module but the order or polarity of one or all
phases is incorrect. In relay settings, go to
Measurement
→
Phasors and check the "System
voltage vectors" diagram. When all connections are correct, the diagram (symmetric feeding)
should look like this:
Settings
Table. 5.2.2 - 25. Settings of the VT scaling.
Name
Range
Step Default
Description
Voltage
measurement
mode
0: 3LN+U4
1: 3LL+U4
2:
2LL+U3+U4
-
0:
3LN+U4
The relay's voltage wiring method. The voltages are scaled according the
set voltage measurement mode.
A
AQ
Q-T215
-T215
Instruction manual
Version: 2.04
72
