GE Multilin
N60 Network Stability and Synchrophasor Measurement System
6-11
6 ACTUAL VALUES
6.3 METERING
6
DELTA-CONNECTED INSTRUMENT TRANSFORMERS:
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.
*
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 N60 displays are always referenced as specified under
SETTINGS
ÖØ
SYSTEM SETUP
ÖØ
POWER SYSTEM
ÖØ
FREQUENCY AND PHASE REFERENCE
.
The example above is illustrated in the following figure.
Figure 6–3: MEASUREMENT CONVENTION FOR SYMMETRICAL COMPONENTS
•
ABC phase rotation:
•
ACB phase rotation:
Table 6–1: SYMMETRICAL COMPONENTS CALCULATION EXAMPLE
SYSTEM VOLTAGES, SEC. V *
VT
CONN.
RELAY INPUTS, SEC. V
SYMM. COMP, SEC. V
V
AG
V
BG
V
CG
V
AB
V
BC
V
CA
F5AC
F6AC
F7AC
V
0
V
1
V
2
13.9
∠
0°
76.2
∠
–125°
79.7
∠
–250°
84.9
∠
–313°
138.3
∠
–97°
85.4
∠
–241°
WYE
13.9
∠
0°
76.2
∠
–125°
79.7
∠
–250°
19.5
∠
–192°
56.5
∠
–7°
23.3
∠
–187°
UNKNOWN (only
V
1 and
V
2
can be determined)
84.9
∠
0°
138.3
∠
–144°
85.4
∠
–288°
DELTA
84.9
∠
0°
138.3
∠
–144°
85.4
∠
–288°
N/A
56.5
∠
–54°
23.3
∠
–234°
V_0
N/A
=
V_1
1
30
–
°
∠
3 3
--------------------
V
AB
aV
BC
a
2
V
CA
+
+
(
)
=
V_2
1 30
°
∠
3 3
-----------------
V
AB
a
2
V
BC
aV
CA
+
+
(
)
=
V_0
N/A
=
V_1
1 30
°
∠
3 3
-----------------
V
AB
a
2
V
BC
aV
CA
+
+
(
)
=
V_2
1
30
–
°
∠
3 3
--------------------
V
AB
aV
BC
a
2
V
CA
+
+
(
)
=
827844A1.CDR
A
B
C
W
YE VTs
1
0
2
A
B
C
DELTA VTs
1
2
SYST
E
M VOLTAG
E
S
SYMM
E
TR
I
CAL
COMPO
NEN
TS
UR phase angle
reference
UR phase angle
reference
UR phase angle
reference
UR phase angle
reference