Ensuring switchgear integrity in high power installations

Abstract

Offshore installations often push switchgear to the limit of their rated current and short-circuit withstand capacity and in some cases even above. This is due to the increase in the number of electrically driven loads and the severe space and weight restrictions offshore. The same is being seen now for onshore installations where there is often limited space for new production facilities. Expansion of existing plants results in both increased rated and short-circuit currents, and in some cases more complex switching arrangements, some of which could cause switchgear ratings to be exceeded. There are several techniques that can be used to cope with such situations. In some cases it is sufficient to provide interlocking to prevent unacceptable operating conditions from occurring. In other cases it is necessary to add pyrotechnic fault current limiters (FCL) to prevent equipment destruction should a short circuit occur. As with all equipment, it is necessary to understand how FCLs operate in order to be sure that they are correctly integrated into the power system. This paper will review several techniques that have been used in applications to ensure switchgear integrity. There is a special focus on the correct integration of FCLs. The authors consider such measures to be an integral part of the switchgear thus allowing verification of all safety features during the equipment design and testing phases prior to arrival at site. The project specifications should include all planned future growth to ensure that the power system and switchgear be designed accordingly.