ABB RET670 Commissioning Manual page 229

1MRK 504 165-UEN A
Transformer protection RET670 2.2 IEC
Commissioning manual
Testing functionality by secondary injection
1. Simulate normal operating conditions with the three-phase currents in phase
with their corresponding phase voltages and with all of them equal to their
rated values.
2. Slowly decrease the measured voltage in one phase until the BLKU signal
appears.
3. Record the measured voltage and calculate the corresponding negative-
sequence voltage according to the equation (observe that the voltages in the
equation are phasors):
3 ⋅ U = U + a 2 ⋅
2 L 1
EQUATION707 V2 EN-US
Where:
U , U and U
L1 L 2 L3
IEC00000275 V1 EN-US
p ×
2
j
= × = -
a 1 e 0, 5
3
IECEQUATION00022 V2 EN-US
4. Compare the result with the set value of the negative-sequence operating
voltage (consider that the set value 3U2> is in percentage of the base voltage
UBase).
5. Repeat steps 1 and 2. Then slowly increase the measured current in one phase
until the BLKU signal disappears.
6. Record the measured current and calculate the corresponding negative-
sequence current according to the equation (observe that the currents in the
equation are phasors):
× = + 2 ×
3 I I a I
2
L 1 L
IECEQUATION00021 V1 EN-US
Where:
,
I I and I
L 1 L 2 L 3
IECEQUATION00020 V1 EN-US
p ×
2
j
= × = -
a 1 e 0, 5
3
IECEQUATION00022 V2 EN-US
7. Compare the result with the set value of the negative-sequence operating
current. Consider that the set value 3I2< is in percentage of the base current
IBase.
U + ⋅ a U
L2 L3
are the measured phase voltages
3
+
. j
2
+ ×
a I
2 L 3
are the measured phase currents
3
+
. j
2
Section 11
(Equation 103)
(Equation 104)
223