Transcript Solution for CCVT live calibration for ERCOT 12-12

HV Field Testing and
CCVT Re-verification
December 2013
CVT Calibration and Re-Verification Circuit
CVT Calibration
Voltage measurement accuracy of 0.05%
of amplitude and 0.05 degrees of phase.
Reference
OVT
0.05%
Class
CVT
Control Room
OVT
Comparator
69 V/
115 V
4 V or 115V
rated
IED
OVT
Electronics
69 V/
115 V
Fiber cable
Copper Cable
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CCVT or PT Calibration
CCVTs or PT
under test
Ref. VTs
connecting
to HV line
(live)
Electronic
comparator
(bridge)
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CCVT or PT Accuracy Re-verification Report
Test report provides:
1. Ratio Error and RCF
(Ratio Correction
Electronic Comparator
(bridge) with < 0.05%
uncertainty traceable to
NIST
Factor)
2. Phase Error, and
3. TCF (Transformer
Correction Factor)
for the CCVT under test at
the real operating voltage,
per IEEE Std. C57.13 and
C57.13.6.
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Extract from
Current/Voltage Sensors for Precise
Measurements of Power Quality in
Distribution Systems for the Smart Grid
Eddy So and Farnoosh Rahmatian
National Research Council Canada and Quanta Technology
IEEE PES General Meeting, Vancouver, BC
July 23, 2013
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Ease of Installation and Use
• Safety
• Light weight
• Easy to connect to HV line
– High-impedance
– Isolation
• Integrated data processing
• Rugged design (environmental elements)
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Traceability
• Unbroken chain of measurements
• Compliance with regulations and standards
• On site calibration / verification of sensors
– The accuracy requirements of the reference system
– Uncertainty < 1/4 devices being verified in the field
• Documentation
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Calibration and Traceability
• Traceability
– Unbroken Chain of Measurements Tracing Back to National and/or
International Standards (e.g., NIST)
– Uncertainty analysis and certification
International
Reference Std
International
Standard
National Standard –
National Labs, e.g.,
NIST, NRC
NIST
Reference Std
Regional or
Portable
References
Ref. A
Device
Under
Test
DUT 1
NRC
Reference Std
Ref. B
DUT 2
Example:
DUT 3
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Ref. C
DUT 4
DUT n
20-50
ppm
200-1000
ppm
0.2 – 1.0%
Calibration Circuit for OVT (OPT)
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Calibration Results for OVT (OPT)
Ratio Error
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Calibration Results for OVT (or OPT)
Phase Error
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Live-line Connections of OVT
• Advantage OVT
– Excitation Current about 1 mA regardless of rated
voltage, as compared to conventional PT
excitation current of about 100 mA to 1 A
(depending on rated voltage).
• Can be connected live
© 2013 - Quanta Technology Canada ULC
OVT Qualification Conclusion
• NRC (NIST) Test Results indicate the suitability
of OVT to be used as reference Instrument
Transformers for live-line on-site calibrations
of HV Revenue Metering Systems of accuracy
class 0.2 – 0.3, including HV PMU Systems
which usually are of accuracy class 0.5 – 1.0.
• Because of its linearity, certain accuracy and
performance parameters can be extended
over harmonics and frequency
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