Based on an analysis of the effects of the current transformer saturation on line current differential protection with breaker-and-a-half configuration

it is concluded that the probability of normal ratio line differential relay's mal-operation will be greatly increased without any extra anti-saturation strategy during an external fault. According to an investigation of the current characteristics in the transformer's linear transform area

a new energy resistance based anti-saturation scheme is proposed which can detect the current transformer saturation and relay's mal-operation during an external fault. Also

a new expression for energy resistance formula is presented which can increase the new scheme's accuracy and sensitivity in breaker-and-a-half configuration. It is shown by simulation results that the scheme proposed can appreciably increase the anti-saturation ability of line current differential protection.