Compensated-current differential relay for protection of transformers

Estimation of Delta Winding Current and Its Application to a Compensated-Current-Differential Relay for a Y-Δ Transformer

“…Once the delta winding current is obtained, the procedure of deriving the modified differential current is the same as [5]. To cope with the remanent flux, the relay obtains the modified differential current separately 'before saturation' and 'during saturation'.…”

“…Once i ab , i bc and i ca are obtained, the modified differential current is estimated using the same technique as in [5]; for clarity, this is briefly described below.…”

“…During magnetic inrush or over-excitation, the relay may mal-operate because the exciting current can be significant but cannot be measured. Kang et al proposed a compensated-currentdifferential relay for transformer protection [5]. The relay uses the same restraining current as a conventional relay, but derives a modified differential current that compensates for both the core-loss and the magnetizing currents.…”

“…A method to estimate the circulating component of the delta winding current is also described. This estimate is then used to modify the differential current, using a similar technique as in [5]. The operating performance of the proposed relay and a conventional current differential relay with harmonic blocking were then evaluated under various EMTP simulated scenarios including magnetic inrush, internal faults and over-excitation.…”

Transmission lines protection based on the current eigenvalues differential concept

“…One of the most important developments for the protection of transmission lines was the current differential relay. This protection was initially used for power transformers and generators [1,2,3,4]. However, with the development of communication and computer technology, this concept was also applied to transmission lines [5,6,7].…”