The next challenge: distance protection designed for ease of application

This paper demonstrates how a distance relay designed for ease of application has fewer settings, and has a lower scope for accidental setting errors. A straightforward "simple-set" mode can allow zone reaches to be applied as percentages of the protected line. The simple-set mode does not artificially place performance constraints on the application, and the use of proven techniques such as delta phase selection and power swing blocking allow universal deployment (for strong and weak infeeds, interconnected, and weakly interconnected systems that may be prone to power swings). Relay settings can be split into two categories: (1) those related to line protection/fault detection, and (2) those to ensure load avoidance. Recent experience from blackouts in several countries shows that the dynamic changes of load may result in undesired operation of distance elements due to the load impedance entering the distance characteristic. A simple and effective load blinding technique as described in this paper forms an effective defence against such unwanted tripping.