ndervoltage (Device 27) tripping of generators was the single biggest identifiable cause of generator tripping during the 2003 blackout. The device 27 measures generator terminal voltage. IEEE Standard C37.102 - IEEE Guide for AC Generator Protection -- does not recommend use of the 27 function for tripping, but only to alarm to alert operators to take necessary actions. Undervoltage alarms as experienced by hydro, fossil, combustion and nuclear units are an indicator of possible abnormal operating conditions such as excitation problems and thermal issues within the unit. Other alarms from RTDs and hydrogen pressure are better indicators of thermal concerns. If function 27 tripping is used for an unmanned facility - the settings must coordinate with the stressed
ndervoltage (Device 27) tripping of generators was the single
biggest identifiable cause of generator tripping during the 2003
blackout. The device 27 measures generator terminal voltage. IEEE
Standard C37.102 - IEEE Guide for AC Generator Protection -- does
not recommend use of the 27 function for tripping, but only to
alarm to alert operators to take necessary actions. Undervoltage
alarms as experienced by hydro, fossil, combustion and nuclear
units are an indicator of possible abnormal operating conditions
such as excitation problems and thermal issues within the unit.
Other alarms from RTDs and hydrogen pressure are better indicators
of thermal concerns. If function 27 tripping is used for an
unmanned facility - the settings must coordinate with the
stressed
