Distance protection is a directional protection scheme based on current and voltage measurements.Its operation is inherently unaffected by system topology or operating conditions

and thus it is widely applied across power lines at various voltage levels.Due to the constant phase angle of positive sequence voltage before and after a fault

it is commonly used as the polarizing voltage to provide strong directionality in distance protection with circular characteristics.However

in systems operating in a single ended power supply mode with an ungrounded neutral

using positive sequence voltage as the polarizing voltage may cause misoperation of distance protection in the event of reverse phase to phase faults on the source side.To address this issue

this paper proposes a blocking criterion for circular distance protection based on logical condiDistance protection is a directional protection scheme based on current and voltage measurements.Its operation is inherently unaffected by system topology or operating conditions

and thus it is widely applied across power lines at various voltage levels.Due to the constant phase angle of positive sequence voltage before and after a fault

it is commonly used as the polarizing voltage to provide strong directionality in distance protection with circular characteristics.However

in systems operating in a single ended power supply mode with an ungrounded neutral

using positive sequence voltage as the polarizing voltage may cause misoperation of distance protection in the event of reverse phase to phase faults on the source side.To address this issue

this paper proposes a blocking criterion for circular distance protection based on logical conditions derived from positive and negative sequence voltage and current measurements.Experimental results demonstrate that the proposed method can effectively prevent false tripping during reverse phase faults

thereby avoiding the escalation of fault impact and enhancing overall system safety.tions derived from positive and negative sequence voltage and current measurements.Experimental results demonstrate that the proposed method can effectively prevent false tripping during reverse phase faults

thereby avoiding the escalation of fault impact and enhancing overall system safety.