GE G60 Instruction Manual page 600

SETTINGS CHAPTER 8: APPLICATION OF SETTINGS
8.2.10.2 100% stator ground
The auxiliary voltage input is required for both the 100% stator ground and the third harmonic neutral undervoltage
elements. Therefore the NEUTRL source needs to be assigned for these elements. Make the following change in the
menu:
SETTINGS  GROUPED ELEMENTS  SETTING GROUP 1  STATOR GROUND
: "SRC 2" (the "NEUTRL" source)
STATOR GROUND SOURCE
This 100% stator ground element provides ground fault protection for the neutral end of the stator winding. The element
has two stages. In this application, stage 1 is used to trip the machine and stage 2 is used for alarm purposes. Set the
pickup to 0.15 for both stages to provide adequate overlap with the auxiliary overvoltage element. Set stage 1 to 0.375 V
secondary (this value can be increased for security in particularly noisy environments). Stage 2 is typically set at 0.3 V
secondary. The supervision settings are expressed in per unit of the setting. The time delay
NOMINAL PHASE VT SECONDARY
settings are five seconds and one second for the Stage 1 and Stage 2 elements respectively.
Eq. 8-31
Make the following changes in the EnerVista software or the front panel
SETTINGS  GROUPED ELEMENTS  SETTING
menu.
GROUP 1  STATOR GROUND  100% STATOR GROUND
8
8.2.10.3 Third harmonic neutral undervoltage
If the phase VTs are delta connected then third harmonic voltage cannot be measured and the 100% stator ground
element cannot be used. In this case, the third harmonic neutral undervoltage element can be used. Field measurements
are taken over the entire operating range of the machine to determine the variation of the third harmonic voltage, such as
shown in the figure.
8-10 G60 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL