Directional comparison blocking system fundamentals

Abstract

We have discussed many practical aspects of directional comparison blocking schemes; its basic implementation with PLC, the pros and cons of non-directional vs. directional starting, coordination time of blocking signal and FP tripping elements, carrier holes, and as well a few of the multitude of implementations seen in practice. We have shown the complexities and necessary considerations for the implementation of a seemingly rather simple, and often taken for granted, DCB scheme. Our intent was not simply to inform the reader but also to motivate the reader to vigorously investigate and “what if” the schemes at use in their utility. Just because “we've always done it this way” isn't a sound basis for how we should proceed in the future with new technology and more flexible protection systems. At the same time, changing just for the sake of change may open a can of worms that the casual user did not anticipate. There is no substitute for careful study and real world experience garnered through event analysis and study.