An adaptive variable window algorithm for transformer differential protection relay

The large-scale transformer protection is one of the most important devices in the protection system of substation and the requiring operating time is limited to 20ms or even less, i.e. A short data window orthogonal filter design method was presented through solving linear matrix equation after analyzing the physical concepts of sampling value phasor in fault signal. It could filter integer or fractional harmonic and guarantee cosine and sine filter possess the same amplitude versus frequency response characteristics. Then the design principle was put forward after analyzing the relationship between frequency property and data window transient responding performance. As an example, the design method was used as the adaptive digital filters for the transformer differential digital transformer differential protection device. The simulation of the algorithm was put forward in the MATLAB software platform. The dynamic test result of the algorithm shows the design method has the good ability for the transformer differential protection especial in transient performance. If it has appropriate settings, it won't be mal-operation on the condition of TA saturation or energizing inrush. The digital transformer differential protection will be improved greatly if this digital filter is used.