Digital differential protection of transformers

Abstract

This chapter gives a brief general review of the principles of transformer differential protection (TDP). This is followed by an explanation of the application of digital techniques and the algorithms that have been developed specifically for the application of transformer protection. The algorithms covered include finite-duration impulse response (FIR) filters, least-squares (LSQ) curve fitting, the digital Fourier algorithm, and the flux-restrained current differential algorithm.Finally, the basic hardware arrangement for implementing digital techniques for the protection of transformers is described. It is, however, important to note that closely similar techniques can be applied to the protection of generators, although, in this case, the transformation ratio of currents is the same on each side of the protected zone.