Although almost all of the generators are synchronous generators set to generate 60/50 Hz electricity,the system frequency is rarely exactly 60/50 Hz Exhibit 0-1 Number of High-Frequency Events by Interconnection(f>60.05 Hz) 10000 Eastern●Vestern◆ERCOT◆Quebec 1000 Exhibit 0-2 Number of Low-Frequency Events by Interconnection(f<59.95) 10000 ◆Eastern。NWestern◆ERCOT◆Quebec 100 1000 802 2003 2004 0 100 802 2003 2004 2005 2006 2007 2008 Year 电力拿镜广城洲量写控制四川省童点实验蜜 家电电力系统广域测量与控制四川省重点实验室  Although almost all of the generators are synchronous generators set to generate 60/50 Hz electricity, the system frequency is rarely exactly 60/50 Hz