GE UR Series Instruction Manual Page 258

Line differential relay.

6.3 METERING
DELTA-Connected Instrument Transformers:
ABC phase rotation:
V_0
=
N/A
1
V_1
=
-------------------- V
3 3
1 30°
V_2
---------------- - V
=
3 3
The zero-sequence voltage is not measurable under the DELTA connection of instrument transformers and is defaulted to
zero. The table below shows an example of symmetrical components calculations for the ABC phase rotation.
Table 6–1: CALCULATING VOLTAGE SYMMETRICAL COMPONENTS EXAMPLE
SYSTEM VOLTAGES, SEC. V *
V
V
V
AG
BG
CG
13.9
76.2
79.7
∠0°
∠–125°
∠–250°
V
UNKNOWN (only
1 and
can be determined)
*
The power system voltages are phase-referenced – for simplicity – to VAG and VAB , respectively. This, however, is a
relative matter. It is important to remember that the UR displays are always referenced as specified under
ÖØ
SYSTEM SETUP
The example above is illustrated in the following figure.
6
Figure 6–3: ILLUSTRATION OF THE UR CONVENTION FOR SYMMETRICAL COMPONENTS
6-10
°
30
2
(
)
+
aV
+
a
V
AB
BC
CA
2
(
)
a
V
aV
+
+
AB
BC
CA
V
V
V
AB
BC
CA
84.9
138.3
85.4
∠–313°
∠–97°
∠–241°
V
84.9
138.3
85.4
2
∠0°
∠–144°
∠–288°
ÖØ
ÖØ
POWER SYSTEM
FREQUENCY AND PHASE REFERENCE
SYSTEM VOLTAGES
A
C
A
C
L90 Line Differential Relay
ACB phase rotation:
V_0
=
N/A
1 30°
(
V_1
---------------- - V
=
3 3
°
1
30
-------------------- V
V_2
=
3 3
VT
UR INPUTS, SEC. V
CONN.
F5AC
F6AC
F7AC
WYE
13.9
76.2
79.7
∠0°
∠–125°
∠–250°
DELTA
84.9
138.3
85.4
∠0°
∠–144°
∠–288°
.
SYMMETRICAL
COMPONENTS
WYE VTs
B
2
DELTA VTs
B
2
6 ACTUAL VALUES
2
)
a
V
aV
+
+
AB
BC
CA
2
(
)
aV
a
V
+
+
AB
BC
CA
SYMM. COMP, SEC. V
V
V
V
0
1
2
19.5
56.5
23.3
∠–192°
∠–7°
∠–187°
N/A
56.5
23.3
∠–54°
∠–234°
SETTINGS
1
0
1
827844A1.CDR
GE Power Management

L90