The Impact of Changing Medium Voltage Switchgear Standards on The Application of Dedicated Motor Buses

A large oil and gas company decided to adopt IEC standards for Medium-Voltage Switchgears. During the front-end engineering design (FEED) stage of various projects, while conducting short-circuit analysis and device-duty evaluation using power-system simulation commercially available software (henceforth will be referred to as software), challenges related to the application of large, direct-on line, motors on dedicated motor buses were faced. The capability of the motor’s circuit breaker to handle the interruption of through-fault currents with high dc offset became an area of concern with the IEC-rated breakers. This put a limitation on how large of a motor can be started across the line in terms of horsepower. This limitation was never faced with the same application when ANSI rated circuit breakers were utilized. A market research and analysis were conducted by reaching out to different manufactures to assure that this limitation will not create obstacles during the detailed-design phase of the project. Results analysis will be presented along with recommendations on how to tackle the technical issues associated with the application of IEC standards on dedicated motor medium-voltage buses.