Correction of Current Transformer Transient Performance

If a current transformer (CT) saturates while transforming the heavy primary current, in each period, there are sections when the magnetic core is unsaturated and transformation is correct, and when it is saturated, it causes enormous errors. The key to correct the errors is to detect instants of sa...

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Bibliographic Details
Published in:IEEE transactions on power delivery 2008-04, Vol.23 (2), p.624-632
Main Authors: Wiszniewski, A., Rebizant, W., Schiel, L.
Format: Article
Language:English
Subjects:
Amplitude estimation
Applied sciences
Circuit faults
Connection and protection apparatus
Contamination
Current measurement
Current transformers
Current-transformer (CT) saturation
Decay
Devices
Direct current
Disturbances. Regulation. Protection
Electrical engineering. Electrical power engineering
Electrical power engineering
Error correction
Exact sciences and technology
Fault currents
Frequency estimation
Magnetic cores
Operation. Load control. Reliability
Power networks and lines
Protection
protective relaying
Saturation
signal reconstruction
Studies
Transformations
Transformers
Transformers and inductors
transient analysis
Unsaturated
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Summary:If a current transformer (CT) saturates while transforming the heavy primary current, in each period, there are sections when the magnetic core is unsaturated and transformation is correct, and when it is saturated, it causes enormous errors. The key to correct the errors is to detect instants of saturation and moments when the saturation ends. This paper presents simple and efficient methods of doing that. In addition, it shows the way how to predict up to three samples after saturation with the acceptable degree of accuracy, thus artificially expanding the unsaturated section. It may substantially facilitate operation of protective devices. The ultimate solution of the problem is to estimate the values of the fundamental frequency component amplitude and the decaying DC component in each period. This paper presents the method of doing that on the ground of four consecutive samples taken during the unsaturated section. If the primary current consists of the fundamental and DC exponential components only, the accuracy of the method is excellent. Neglecting contamination of the current signal with harmonics and noise, it is possible to reconstruct the CT primary current based on the measured values of fundamental and DC components.
ISSN:0885-8977
1937-4208
DOI:10.1109/TPWRD.2008.915832