A method for evaluating loadability of incremental-quantity distance elements

This paper presents a method for evaluating the loadability of incremental-quantity distance (TD21) protection elements. Responding to changes in voltages and currents, the TD21 elements are not impacted by heavy load or power swings. However, switching operations that result in sudden changes in load, including both load pickup and load rejection, may impact security of the TD21 elements. Traditional methods of evaluating protection element loadability do not apply to incremental quantity-based protection elements and schemes. This paper closes the gap by introducing a simple and practical method of evaluating TD21 loadability. The paper provides a short overview of the key TD21 design details and describes a TD21 loadability evaluation method.