GE D30 Instruction Manual page 419

CHAPTER 6: ACTUAL VALUES
DELTA-connected instrument transformers
• ABC phase rotation:
V_0 = N/A
1 ∠ 30 °
–
V_1 = ------------------ V (
AB
3 3
∠
1 30°
V_2 = --------------- V (
AB
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: Symmetrical components calculation example
SYSTEM VOLTAGES, sec. V *
V V V
AG BG CG
13.9 76.2 79.7
∠0° ∠–125° ∠–250°
UNKNOWN (only V and V
1 2
can be determined)
* The power system voltages are phase-referenced – for simplicity – to V
relative matter. It is important to remember that the D30 displays are always referenced as specified under
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
C
C
D30 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
2
+ aV + a V )
BC CA
2
+ a V + aV )
BC CA
VT conn. relay INPUTS, sec. V
V V V
AB BC CA
84.9 138.3 85.4 WYE
∠–313° ∠–97° ∠–241°
84.9 138.3 85.4 DELTA
∠0° ∠–144° ∠–288°
SYSTEM VOLTAGES
A
A
• ACB phase rotation:
V_0 = N/A
1 30° ∠
V_1 = --------------- V (
AB
3 3
∠ °
1 30
–
V_2 = ------------------ V (
3 3
F5ac F6ac F7ac
13.9 76.2 79.7
∠0° ∠–125° ∠–250°
84.9 138.3 85.4
∠0° ∠–144° ∠–288°
and V , respectively. This, however, is a
AG AB
.
SYMMETRICAL
COMPONENTS
WYE VTs
B
2
DELTA VTs
B
2
827844A1.CDR
METERING
2
+ a V + aV )
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
6
6-13