Directional overcurrent relaying (67) refers to relaying that can use the phase relationship of voltage and current to determine direction to a fault. There are a variety of concepts by which this task is done. This paper will review the mainstream methods by which 67 type directional decisions are made by protective relays. The paper focuses on how a numeric directional relay uses the phase relationship of sequence components such as positive sequence (V 1 vs. I 1 ), negative sequence (V 2 vs. I 2 ), and zero sequence (V 0 vs. I 0 ) to sense fault direction, but other concepts such as using quadrature voltage (e.g., V AB vs I C ) are included. Index Terms: directional relaying, sequence component, negative sequence, zero sequence, 67, 32, quadrature voltage. AUTHOR BIOGRAPHYJohn Horak (M,1987) received his BSEE in 1987 from the University of Houston and an MSEE in the field of power system analysis in 1995 from the University of Colorado. He has worked for Houston Lighting and Power, Chevron, and Stone and Webster Engineering, where he spent several years on assignment in the System Protection Engineering offices of Public Service Company of Colorado. In 1997 he began his present position as an Application Engineer for Basler Electric.

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Directional overcurrent relaying (67) refers to relaying that can use the phase relationship of voltage and current to determine direction to a fault. There are a variety of concepts by which this task is done. This paper will review the mainstream methods by which 67 type directional decisions are made by protective relays. The paper focuses on how a numeric directional relay uses the phase relationship of sequence components such as positive sequence (V 1 vs. I 1 ), negative sequence (V 2 vs. I 2 ), and zero sequence (V 0 vs. I 0 ) to sense fault direction, but other concepts such as using quadrature voltage (e.g., V AB vs I C ) are included.Index Terms: directional relaying, sequence component, negative sequence, zero sequence, 67, 32, quadrature voltage. AUTHOR BIOGRAPHIESJohn Horak (M,1987) received his BSEE in 1987 from the University of Houston and an MSEE in the field of power system analysis in 1995 from the University of Colorado. He has worked for Houston Lighting and Power, Chevron, and Stone and Webster Engineering, where he spent several years on assignment in the System Protection Engineering offices of Public Service Company of Colorado. In 1997 he began his present position as an Application Engineer for Basler Electric. Walt Babic (M,2003) received his BSEE from Rensselaer PolytechnicInstitute in the field of electrical engineering and an MS from Union College in Schenectady, New York, in the field of power systems. He worked more than 30 years for General Electric in system sales engineering, application engineering, and project management positions, with a protective relay focus. In 2001 he began his present position as an Application Engineer for Basler Electric and continues his involvement in protective relay applications.

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