High power electrical systems for air separation plants

There is a need for reliable, efficient and safe high power electrical systems in the petrochemical industry e.g. for air separation/oxygen plants. Such air separation plants use large synchronous motors. These motors cannot be started directly on line and a specialized redundant, cost effective, static frequency converter start system is proposed for a number of such trains. Redundancy is built in to meet availability requirements. Unique motor excitation systems are essential to meet reliability, soft start and ride-through requirements. The high power ratings require an advanced distribution network and associated switchgear design to manage fault levels while meeting system stability requirements. Specialised automation and protection systems are required to cater for various plant conditions. Overall electrical design, construction, testing, commissioning and operation experience are described for two of the world's largest air separation plants (100 MVA each) with synchronous motors rated up to 55 MW. The lessons learned from the first plant are overviewed and subsequently integrated to achieve an optimised design for the second plant. Associated electrical equipment design improvements are outlined. It is shown how the key challenges were effectively addressed proven by test and operation experience results.