réductions de tension tournantes

CONT: Sags/Brownouts ... Short term decreases in voltage levels. This is the most common power problem, accounting for 87 percent of all power disturbances according to a study by Bell Labs. ... Typically, sags are caused by the start-up power demands of many electrical devices (including motors, compressors, elevators, shop tools, other office equipment, etc.). Utilities also create sags as a means of coping with extraordinary power demands, like high air conditioner use on a steamy summer's day. In a procedure known as ""rolling brownouts,"" the utility will systematically lower voltage levels in certain areas for hours or days at a time.