GE C70 Instruction Manual page 470

METERING
DELTA-connected instrument transformers
• ABC phase rotation:
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: Symmetrical components calculation example
SYSTEM VOLTAGES, sec. V *
V V
AG BG
13.9 76.2
∠0° ∠–125°
V
UNKNOWN (only
1
can be determined)
* The power system voltages are phase-referenced – for simplicity – to V
relative matter. It is important to remember that the C70 displays are always referenced as specified under
SYSTEM SETUP  POWER SYSTEM  FREQUENCY AND PHASE REFERENCE
The example above is illustrated in the following figure.
6
6-14
V V V V
CG AB BC
79.7 84.9 138.3 85.4
∠–250° ∠–313° ∠–97° ∠–241°
V
and 84.9 138.3 85.4
2
∠0° ∠–144° ∠–288°
Figure 6-4: Measurement convention for symmetrical components
• ACB phase rotation:
VT conn. relay INPUTS, sec. V
F5ac F6ac
CA
WYE 13.9 76.2
∠0° ∠–125°
DELTA 84.9 138.3
∠0° ∠–144°
and V
AG
.
C70 CAPACITOR BANK PROTECTION AND CONTROL SYSTEM – INSTRUCTION MANUAL
CHAPTER 6: ACTUAL VALUES
SYMM. COMP, sec. V
F7ac V V
0 1
79.7 19.5 56.5
∠–250° ∠–192° ∠–7°
85.4 N/A 56.5
∠–288° ∠–54°
, respectively. This, however, is a
AB
SETTINGS 
V
2
23.3
∠–187°
23.3
∠–234°