Angle output name
Angle value
Possible reason if not OK
I_ANGL_C1_C2
±180
OK
I_ANGL_A1_A3
±180
OK
I_ANGL_B1_B3
±180
OK
I_ANGL_C1_C3
±180
OK
Table 670: Angle outputs when settings CT connection 1-2 and CT connection 1-3
match the actual CT connections on windings 1, 2 and 3 but the phase B polarity is
wrong compared to other phases on winding 2
Angle output name
Angle value
Possible reason if not OK
I_ANGL_A1_B1
+120
OK
I_ANGL_B1_C1
+120
OK
I_ANGL_C1_A1
+120
OK
I_ANGL_A2_B2
–60
Wrong polarity phase B
I_ANGL_B2_C2
–60
Wrong polarity phase B
I_ANGL_C2_A2
+120
OK
I_ANGL_A3_B3
+120
OK
I_ANGL_B3_C3
+120
OK
I_ANGL_C3_A3
+120
OK
I_ANGL_A1_A2
±180
OK
I_ANGL_B1_B2
0
Winding 2, wrong polarity
phase B
I_ANGL_C1_C2
±180
OK
I_ANGL_A1_A3
±180
OK
I_ANGL_B1_B3
±180
OK
I_ANGL_C1_C3
±180
OK
4.3.3.8
Recommendations for current transformers
The more important the object to be protected, the more attention should be
paid to the CTs. Normally, it is not possible to dimension the CTs so that they
repeat currents with high DC components without saturating when the residual
flux of the current transformer is high. TR3PTDF operates reliably even though
the CTs are partially saturated. The purpose of the following current transformer
recommendations is to secure the stability of the relay at high through-currents and
the quick and sensitive operation of the relay at faults occurring in the protected
area where the fault currents can be high.
The accuracy class recommended for CTs to be used with TR3PTDF is 5P, where the
limit of the current error at the rated primary current is 1 percent and the limit of
the phase displacement is 60 minutes. The limit of the composite error at the rated
accuracy limit primary current is 5 percent.
The approximate value of the accuracy limit factor F
a
corresponding to the actual
CT burden can be calculated on the basis of the rated accuracy limit factor F
n
(ALF)
1MRS759142 F
Protection functions
REX640
Technical Manual
739