Agenda
Current Transformers
Transformer Ratio
Polarity
IEEE Metering Accuracy
IEEE Relaying Accuracy
Accuracy Influencing factors
Burden Calculation
Rating Factor
Voltage Transformers
IEEE Accuracy Classes
Installation Guidelines
Required Information for Specifying CTs &
VTs
“Take Home Rules” for CTs & VTs
IEEE CT Metering Accuracy
Accuracy Class ( * )
Application
0.15 High Accuracy Metering
0.15S “Special” High Accuracy Metering
0.3 Revenue Metering
0.6 Indicating Instruments
1.2 Indicating Instruments
* All accuracy classes defined by IEEE C57.13 or C57.13.6
* Accuracy classes include both ratio & phase angle error
IEEE CT Metering Accuracy
Burden
Load connected to CT secondary
Includes devices & connecting leads
Expressed in ohms
Standard values = B0.1, B0.2, B0.5, B0.9, B1.8
E0.04, E0.2
All burdens defined by IEEE C57.13 or C57.13.6 for 60 Hz only
8
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