Distance digital algorithm immune to saturation of current transformers

Saturation of current transformers (CT) may introduce errors in operation of distance relays. To avoid the errors only the current phasors in the intervals should be calculated when the CT is unsaturated. The proposed algorithm calculates phasors of the current, utilizing algorithms with variable data window. The first results are obtained after the third sample of the fault current, so the calculation may be completed before the current transformer saturates. The algorithm is repeated in each cycle, during intervals of nonsaturation. The errors in calculation the amplitude of the primary current fundamental component is less than 10%, while the phase angle error is smaller than 4 deg., even if the current transformer is very severely saturated