A CT Saturation Detection Algorithm Using Secondary Current Third Difference Function
Rajnish Prasad Pandey,  Dr. R. N. Patel
This paper proposes an algorithm for detecting current transformer (CT) saturation by analyzing a secondary current. The current has point of inflection where saturation begins and ends. Then, discontinuity in the first difference of the current arises at the next instants of points of inflection, where the second and third differences of the current may have large values enough to detect saturation. In this paper third difference is used because it is more effective than second difference in terms of saturation detection. Ideally the function of current transformer is to transform and reproduce the primary current in the secondary circuit in a most faithful manner. Practically, some distortion in ratio and phase angle can be tolerated. How much of these distortions can be tolerated depend upon the application for which the CT is being used. These allowable errors are specified in different standards. Under normal operating conditions CT reproduces the primary current in the secondary side with good degree of accuracy, however, during abnormal operating conditions CT is likely to get saturated. A current transformer (CT) can saturate, for various reasons, like: attempting to transform heavy primary fault currents, heavy burden on the secondary side of current transformer or transient DC offset in the primary fault current. The method for CT saturation detection that has been simulated is, An algorithm for detecting CT saturation using second current third difference function.
Keywords- Current Transformer Saturation, difference, point of inflection, remanent flux
Cite this Article
Rajnish Prasad Pandey,  Dr. R. N. Patel,   "A CT Saturation Detection Algorithm Using Secondary Current Third Difference Function"
, International Journal of Engineering Development and Research (IJEDR), ISSN:2321-9939, Volume.2, Issue 2, pp.2774-2779, June 2014, Available at :http://www.ijedr.org/papers/IJEDR1402236.pdf