The improvement in the reliability problem for air current breaker´s over current protect function

Almost all plants have the experience of ACB´s overcurrent relay (OCR) unexpectedly trip event. Each accident will cause a huge production loss. But manufacturers of OCR can´t afford the cost-effective solution of problem. The most used solution is to install an additional relay (ex. ABB Relay B) to replace the function of the ACB´s OCR or to adopt a new ACB to replace the old one. These two uneconomical solutions are not only high cost but also time consumption on annual PM. Thus, authors proposed a novel solution by interlocking the main ACB´s relay and the feeder ACB´s OCR function to prevent the ACB tripped by OCR false tripping signal. This method does not require additional relay and current transformer. Therefore, it is a cost-effective and time saving solution.