Note that the operation of this feature is based on current peak value. That
means that this overcurrent function is also able to trip for the same current
magnitude but for different injected frequencies. If required repeat this
injection procedure for example for the 3rd harmonic by just simply
injecting 3 · 50 = 150Hz currents with the same magnitude. Obtain results
shall be the same.
Undercurrent feature
1. Inject SCB rated current (that is, 0.587A at 50Hz for this SCB) in all three phases.
2. Lower phase A current 10% under the set value for setting parameter PU_37 (that is,
0.9 · 0.7 · 0.587A = 0.370A at 50Hz for this SCB).
3. Check that function binary output signals PU_37_A and PU_UC are set to one.
4. Check that function binary output signals TRUC and TRIP are set to one after the set
time under parameter tUC (for example, 5s for this SCB) has expired.
5. If any of these signals are used for tripping, signaling and/or local/remote indication
check that all relevant contacts and LEDs have operated and that all relevant
GOOSE messages have been sent.
6. Check that service value from the function for current in phase A, on the local HMI
under Main menu/Test is approximately 185A (that is, 0.370A · (500/1) = 185A).
7. Stop injection of all currents (that is, set all currents back to 0A).
8. Check that all above mentioned function binary output signals now have logical
value zero because they will be automatically blocked by operation of built-in
reconnection inhibit feature.
9. Repeat above steps 1-8 for phase B and phase C.
Reactive power overload feature
Note that during testing the reactive power overload feature the harmonic
voltage overload feature or overcurrent feature may also give pickup and
trip signals depending on their actual settings. Therefore it is
recommended to switch them off during this test.
1. Inject current equal to the set reactive power overload pickup level under setting
parameter UP_QOL (that is, 1.3 · 0.587A = 0.763A at 50Hz for this SCB) in phase
A only.
2. Check that function binary output signals PU_QOL_A and PU_QOL are set to one.
3. Check that function binary output signals TRQOL and TRIP are set to one after the
set time under parameter tQOL (for example, 60s for this SCB) has expired.
1MRK 504 165-UUS - Section 11
Testing functionality by secondary injection
Transformer protection RET670 2.2 ANSI 203
Commissioning manual
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