Directional Overcurrent Relaying (67) Concepts

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 reviews 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 (V₁ vs. I₁), negative sequence (V₂ vs. I₂), and zero sequence (V₀ vs. I₀) to sense fault direction, but other concepts such as using quadrature voltage (e.g., V_ab vs I_c) are included