Now the commonly used starting elements are insensitivity to the slow expansibility faults,and high earth resistance faults are easily affected by power system swing.

• 现有微机保护装置的启动元件存在着高阻接地和缓慢发展性故障情况下灵敏度不足的缺点,振荡情况下可能产生误启动,并且不能识别振荡中再发生故障的情况。