A novel CT saturation identification scheme for differential protection of generators

A new CT saturation block scheme for generator differential protection implemented with mathematical morphology filter is presented. By use of the excellent singularity detecting together with the noise-repressing abilities, the time difference between fault occurrence and differential current emergence instant can be extracted in real time with very high accuracy in terms of the multi-resolution morphological gradient. It is thus possible to set a rational threshold of this time difference to identify the CT saturation due to the external fault with very high through current from any internal fault even though it may be accompanied by CT saturation as well. The EMTDC based simulation results show that the scheme can effectively prevent generator differential protection from mal-operating caused by high through current and thus CT saturations.