GE Multilin T60 Transformer Protection System 6-15
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 T60 displays are always referenced as specified under
SETTINGS
SYSTEM SETUP POWER SYSTEM 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
130–
33
--------------------
V
AB
aV
BC
a
2
V
CA
++=
V_2
130
33
-----------------
V
AB
a
2
V
BC
aV
CA
++=
V_0 N/A=
V_1
130
33
-----------------
V
AB
a
2
V
BC
aV
CA
++=
V_2
130–
33
--------------------
V
AB
aV
BC
a
2
V
CA
++=
827844A1.CDR
A
B
C
WYE VTs
1
0
2
A
B
C
DELTA VTs
1
2
SYSTEM VOLTAGES SYMMETRICAL
COMPONENTS
UR phase angle
reference
UR phase angle
reference
UR phase angle
reference
UR phase angle
reference
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