When injecting the currents in the high voltage winding, the angle values
I_ANGL_A1_B1, I_ANGL_B1_C1, I_ANGL_C1_A1, I_ANGL_A2_B2, I_ANGL_B2_C2
and I_ANGL_C2_A2 have to show +120 deg. Otherwise the phase order can be
wrong or the polarity of a current transformer differs from the polarities of the
other current transformers on the same side.
If the angle values I_ANGL_A1_B1, I_ANGL_B1_C1 and I_ANGL_C1_A1 show -120
deg, the phase order is wrong on the high voltage side. If the angle values
I_ANGL_A2_B2, I_ANGL_B2_C2 and I_ANGL_C2_A2 show -120 deg, the phase order
is wrong on the low voltage side. If the angle values I_ANGL_A1_B1, I_ANGL_B1_C1
and I_ANGL_C1_A1 do not show the same value of +120, the polarity of one current
transformer can be wrong. For instance, if the polarity of the current transformer
measuring IL2 is wrong, I_ANGL_A1_B1 shows -60 deg, I_ANGL_B1_C1 shows -60
deg and I_ANGL_C1_A1 shows +120 deg.
When the phase order and the angle values are correct, the angle values
I_ANGL_A1_A2, I_ANGL_B1_B2 and I_ANGL_C1_C2 usually show ±180 deg. There
can be several reasons if the angle values are not ±180 deg. If the values are 0 deg,
the value given for
CT connection type
is probably wrong. If the angle values are
something else, the value for
Clock number
can be wrong. Another reason is that the
combination of
Winding 1 type
and
Winding 2 type
does not match
Clock number
.
This means that the resulting connection group is not supported.
Example
If
Winding 1 type
is set to "Y",
Winding 2 type
is set to "y" and
Clock number
is set to "Clk num 1", the resulting connection group "Yy1" is not a supported
combination. Similarly if
Winding 1 type
is set to "Y",
Winding 2 type
is set to
"d" and
Clock number
is set to "Clk num 0", the resulting connection group
"Yd0" is not a supported combination. All the non-supported combinations
of
Winding 1 type
,
Winding 2 type
and
Clock number
settings result in the
default connection group compensation that is "Yy0".
4.3.2.7 CT connections and transformation ratio correction
The connections of the primary current transformers are designated as "Type 1" and
"Type 2".
• If the positive directions of the winding 1 and winding 2 protection relay
currents are opposite, the
CT connection type
setting parameter is "Type 1". The
connection examples of "Type 1" are as shown in
Figure 401
and
Figure 402
.
• If the positive directions of the winding 1 and winding 2 protection relay currents
equate, the
CT connection type
setting parameter is "Type 2". The connection
examples of "Type 2" are as shown in
Figure 403
and
Figure 404
.
• The default value of the
CT connection type
setting is "Type 1".
Protection functions
1MRS759142 F
706 REX640
Technical Manual
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