Abstrakt

Modeling Of Power Transformer for Differential Protection Using PSCAD

L.Madhan kumar , R.Murugan , Dr. S. Chandramoghan

The differential protection of power transformer is a unit protection scheme. The protective scheme for power transformer should operate only for the internal fault, and it must be insensitive for any fault outside the zone of protection. That means the protection scheme should not operate for any external through fault and the magnetizing inrush current due to energization of the transformer under no load condition and also due to external fault removal. Transformer inrush currents are high-magnitude, harmonic-rich currents generated when transformer cores are driven into saturation during energization. These currents have undesirable effects, including potential damage or loss-of-life to the transformer, protective relay mal-operation and reduced power quality on the system. In power transformer differential protection second and fifth harmonics are analyzed using Fast Fourier Transform (FFT) technique to provide the dual slope differential relay operating chartrictics. The relay logic and the algorithm that uses fast fourier transform for extraction of fundamental and higher harmonics components of differential current which are used to block the Inrush current. The simulations were performed using PSCAD Simulation software. The proposed systems can be used to test new transformer differential protection algorithms and the actual differential relays available on the market.