GE C70, Instruction Manual

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GE Multilin C70 Capacitor Bank Protection and Control System 6-13
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 C70 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
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
WYE VTs
1
0
2
A
B
C
DE LTA 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