28-12-2012, 12:54 PM
Busbar differential protection with a CT compensating algorithm
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ABSTRACT
The design ,evaluation and implementation of a busbar differential protection relay that operates in conjunction with CT compensating algorithm are described .prior to saturation ,the secondary current of a CT is not compensated . The compensating algorithm detects the start of first saturation on the basis of the third difference function of the current and estimate the core flux at the first saturation start by inserting value of third difference function of the current in to the magnetization curve of the CT .Thereafter ,it calculate the core flux and then corresponding magnetizing current in conjunction with the magnetization curve. The calculated magnetizing current is added to the measured secondary current to obtain the correct secondary current .The algorithm can estimate correct secondary current .