Schneider Electric PM870 Manual De Usuario
PowerLogic
TM
Series 800 Power Meter
63230-500-225A2
Appendix A—Instrument Transformer Wiring: Troubleshooting Tables
3/2011
© 2011 Schneider Electric All Rights Reserved
78
Field Example
Readings from a 4-wire system
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lag to
lead fluctuating
Troubleshooting Diagnosis
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Power factors cannot be correct .
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None of the “Section II” symptoms exist, so proceed to the 4-wire troubleshooting
(“Section IV”).
(“Section IV”).
•
Cannot calculate kW because 3-phase power factor cannot be right, so calculate kVA
instead.
instead.
•
Calculated kVA =
=
=
=
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Power meter reading is essentially zero compared to this value.
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4-wire Case E looks similar.
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Since the PTs were connected to other power meters which were reading correctly,
suspect two CT leads swapped.
suspect two CT leads swapped.
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Since A-phase power factor is the only one that has a normal looking lagging value,
suspect B and C-phase CT leads may be swapped.
suspect B and C-phase CT leads may be swapped.
•
After swapping B and C-phase CT leads, all readings went to the expected values;
problem solved.
problem solved.
kW
25
=
kVAR
15
–
=
kVA
27
=
I
A
904A
=
I
B
910A
=
I
C
931A
=
I
3
Avg
908A
=
V
AB
495V
=
V
BC
491V
=
V
CA
491V
=
V
AN
287V
=
V
BN
287V
=
V
CN
284V
=
PF
3
Avg
0.75
=
0.22
3 V
ab
I
3
Avg
1000
1.732 495 908
1000
778 kVA
778 kVA