Electric equipment such as computers, servers, switches, routers and data storage devices require absolute continuity of electric supply. Any blackout can cause significant financial losses. Cooling systems, which may account for up to 45 % of the total load in data centers, may consist of significant non-linear loads in terms of variable speed drives. Along with other non-linear loads, they will create harmonic distortions. High harmonic distortions are a well-known source of nuisance tripping and process interruptions. Process interruption may also arise from power outages or voltage sags from power grids. Power protection is a key consideration in the design of reliable and profitable data centers.