Recommendations For Current Transformers - ABB RELION 620 Series Technical Manual

Section 4
Protection functions
4.6.2.7
446
Angle output name
I_ANGL_A1_A3
I_ANGL_B1_B3
I_ANGL_C1_C3
Table 343: Angle outputs when settings CT connection 1-2 and CT connection 1-3 match with the
actual CT connections on winding 1, 2 and 3 but the phase B polarity is wrong compared to
other phases on winding 2
Angle output name
I_ANGL_A1_B1
I_ANGL_B1_C1
I_ANGL_C1_A1
I_ANGL_A2_B2
I_ANGL_B2_C2
I_ANGL_C2_A2
I_ANGL_A3_B3
I_ANGL_B3_C3
I_ANGL_C3_A3
I_ANGL_A1_A2
I_ANGL_B1_B2
I_ANGL_C1_C2
I_ANGL_A1_A3
I_ANGL_B1_B3
I_ANGL_C1_C3

Recommendations for current transformers

The more important the object to be protected, the more attention should be paid to the
current transformers. Normally, it is not possible to dimension the current transformers so
that they repeat currents with high DC components without saturating when the residual
flux of the current transformer is high. 87T operates reliably even though the current
transformers 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 current transformers to be used with 87T is 5P, in
which the limit of the current error at the rated primary current is 1 percent and the limit
Angle value Possible reason if not Ok
±180 Ok
±180 Ok
±180 Ok
Angle value Possible reason if not Ok
+120 Ok
+120 Ok
+120 Ok
-60 Wrong polarity phase B
-60 Wrong polarity phase B
+120 Ok
+120 Ok
+120 Ok
+120 Ok
±180 Ok
0 Winding 2, wrong polarity phase B
±180 Ok
±180 Ok
±180 Ok
±180 Ok
1MAC504801-IB E
620 series ANSI
Technical Manual