PowerLogic Knowledge Base Procedure
Phasor Diagram Verification - 3 wire system
Safety Precautions
•
•
•
Work on De-Energized Gear
NEVER short circuit the secondary of a PT
NEVER open circuit a CT
Use the shorting block to short circuit the leads of the CT before removing the
connection from the CM.
Procedure
1. Follow Phasor Diagram Data Reading procedure
2. Draw each of the vectors in the diagram or complete the Phasor Diagram Creator
spreadsheet, 3-wire Tab
Example:
200
3-Wire
Current
Phase A
Phase B
Phase C
Neutral
Voltage
Phase A-B
Phase B-C
Phase C-A
Phase A-N
Phase B-N
Phase C-N
150
Magnitud Register Angle
1078
79 1079 291.5
1080
81 1081 164.8
1082
72 1083
46.7
1084
1085
Register
100
50
0
1094
1096
1098
1088
1090
1092
210
207
207
1095
1097
1099
1089
1091
1093
0
239.9
120.5
-150
-100
-50
0
50
100
150
200
250
-50
-100
-150
-200
Ia
Ib
Ic
Vab
Vbc
Vca
3. Determine if your system has positive or negative phase rotation and compare your
diagram with the possible cases attached. Positive rotation guidelines are shown on
page 2 and negative rotation guidelines on page 3.
Note
•
•
Voltage between Va and Vb is the 0 degree reference
ALL other phasors are referenced from these phasors
Phasor_Diagram_Verification_3_wire.doc
 2000 Square D Company, All Rights Reserved
Rev:08/3/2000
1 of 7
PowerLogic Knowledge Base Procedure
Possible Cases
200
150
Vca (120)
ABC or Positive
Phase Rotation
100
50
Vab (0)
0
-150
-100
-50
0
50
100
150
200
250
-50
Vbc (240)
CCW
Phasor Sequence Convention
Ia
Ib
Ic
Vab
Vbc
Vca
-100
-150
-200
0.87 Lead PF, Capacitive Load
200
200
150
150
100
100
50
50
0
-200
-100
0
0
100
200
300
-50
-100
-150
-200
-200
-100
0
100
200
300
-50
Ia
Ib
Ic
Vab
Vbc
Vca
Unity PF, Resistive Load
Phasor_Diagram_Verification_3_wire.doc
 2000 Square D Company, All Rights Reserved
-100
-150
-200
Ia
Ib
Ic
Vab
Vbc
Vca
0.87 Lag. PF, Inductive Load
Rev:08/3/2000
2 of 7
PowerLogic Knowledge Base Procedure
Vbc (120)
ACB or Reverse
Phase Rotation
200
150
Vab (0)
100
50
Vca (240)
CCW
Phasor Sequence Convention
0
-200
-100
0
100
200
300
-50
Ia
Ib
Ic
Vab
Vbc
Vca
-100
-150
-200
0.87 Lead PF Capacitive Load
200
200
150
150
100
100
50
50
0
-200
-100
0
0
100
300-150
200
-150
-200
-50
0
50
100
150
200
250
-50
-50
-100
-100
Ia
Ib
Ic
Vab
Vbc
Vca
Unity PF, Resistive Load
Phasor_Diagram_Verification_3_wire.doc
 2000 Square D Company, All Rights Reserved
-100
-150
-200
Ia
Ib
Ic
Vab
Vbc
Vca
0.87 Lag. PF, Inductive Load
Rev:08/3/2000
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PowerLogic Knowledge Base Procedure
4. Use the following rules to match your system to one of the possible cases
• To change phasor direction: revert polarity of PT/CT
Example:
200
The polarity of CT phase b is
reversed
150
Reversing the polarity of the
CT will correct the phasor with
a shift of 180 degrees
100
50
0
-150
-100
-50
0
50
100
150
200
250
-50
Ia
Ib
Ic
Vab
Vbc
Vca
-100
-150
-200
•
To change phases: swap CT/PT
Example:
200
The leads from the CTs for A and
C phases were swapped on the
input terminals of the circuit
monitor
150
100
50
0
-200
Swapping the phase A&C CT
leads on the current input
terminal of the circuit monitor
will correct this condition
-100
0
100
200
-100
-150
-200
•
•
300
-50
Ia
Ib
Ic
Vab
Vbc
Vca
Do one change at a time
Repeat Checking Meter Readings procedure after you finish changing connections
Phasor_Diagram_Verification_3_wire.doc
 2000 Square D Company, All Rights Reserved
Rev:08/3/2000
4 of 7
PowerLogic Knowledge Base Procedure
Examples of Voltage swaps (Positive Sequence)
A swapped with B, B swapped with C, C swapped with A
200
3-Wire
Current
Phase A
Phase B
Phase C
Neutral
Register
Voltage
Phase A-B
Phase B-C
Phase C-A
Phase A-N
Phase B-N
Phase C-N
1078
1080
1082
1084
150
Magnitud Register Angle
150 1079
53.2
150 1081
285
150 1083
172
1085
100
50
0
1094
1096
1098
1088
1090
1092
210
207
207
1095
1097
1099
1089
1091
1093
0
240.9
120.4
-200
-150
-100
-50
0
50
100
150
200
250
-50
-100
Ia
Ib
Ic
Vab
Vbc
Vca
-150
-200
Voltage swaps: A swapped with B
200
3-Wire
Current
Phase A
Phase B
Phase C
Neutral
Voltage
Phase A-B
Phase B-C
Phase C-A
Phase A-N
Phase B-N
Phase C-N
Register
1078
1080
1082
1084
Magnitud
150
150
150
150
Register
1079
1081
1083
1085
Angle
112
344.1
231.8
100
50
0
1094
1096
1098
1088
1090
1092
210
207
207
1095
1097
1099
1089
1091
1093
0
120.8
239.7
-150
-100
-50
0
100
150
200
-50
-100
-150
-200
Phasor_Diagram_Verification_3_wire.doc
 2000 Square D Company, All Rights Reserved
50
Rev:08/3/2000
Ia
Ib
Ic
Vab
Vbc
Vca
5 of 7
250
PowerLogic Knowledge Base Procedure
Examples of Voltage swaps (Positive Sequence)- Continued
Voltage swaps: A swapped with C
200
3-Wire
Current
Phase A
Phase B
Phase C
Neutral
Voltage
Phase A-B
Phase B-C
Phase C-A
Phase A-N
Phase B-N
Phase C-N
Register
1078
1080
1082
1084
150
Magnitud Register Angle
150 1079 232.8
150 1081 107.2
150 1083 351.5
1085
100
50
0
1094
1096
1098
1088
1090
1092
210
207
207
1095
1097
1099
1089
1091
1093
0
120.2
240.6
-150
-100
-50
0
50
100
150
200
250
-50
-100
Ia
Ib
Ic
Vab
Vbc
Vca
-150
-200
Voltage swaps: B swapped with C
200
3-Wire
Current
Phase A
Phase B
Phase C
Neutral
Voltage
Phase A-B
Phase B-C
Phase C-A
Phase A-N
Phase B-N
Phase C-N
Register
1078
1080
1082
1084
150
Magnitud Register Angle
150 1079 351.4
150 1081 223.2
150 1083 110.5
1085
100
50
0
1094
1096
1098
1088
1090
1092
210
207
207
1095
1097
1099
1089
1091
1093
0
119.3
239.5
-150
-100
-50
0
100
150
200
250
-50
-100
-150
-200
Phasor_Diagram_Verification_3_wire.doc
 2000 Square D Company, All Rights Reserved
50
Rev:08/3/2000
Ia
Ib
Ic
Vab
Vbc
Vca
6 of 7
PowerLogic Knowledge Base Procedure
Examples of Voltage swaps (Positive Sequence) - Continued
Voltage swaps: A swapped with C, C swapped with B, B swapped with A
200
3-Wire
Current
Phase A
Phase B
Phase C
Neutral
Voltage
Phase A-B
Phase B-C
Phase C-A
Phase A-N
Phase B-N
Phase C-N
Register
1078
1080
1082
1084
150
Magnitud Register Angle
150 1079 170.8
150 1081
42
150 1083 289.9
1085
100
50
0
1094
1096
1098
1088
1090
1092
210
207
207
1095
1097
1099
1089
1091
1093
0
239.2
119.3
-200
-150
-100
-50
0
100
150
200
250
-50
-100
-150
-200
Phasor_Diagram_Verification_3_wire.doc
 2000 Square D Company, All Rights Reserved
50
Rev:08/3/2000
Ia
Ib
Ic
Vab
Vbc
Vca
7 of 7