Stator Differential; Generator Unbalance - GE G60 Instruction Manual

9 APPLICATION OF SETTINGS
The "LINE" and "NEUTRL" sources are both required for the stator differential element. The minimum pickup can usually be
set as low as 0.05 pu (corresponding to 0.25 A secondary or 400 A primary in this example). Set the
setting to accommodate for CT errors; a setting of 10% is adequate in most instances. Set the
to accommodate for errors due to CT saturation; a setting of 80% is recommended for most applications. The
setting must be greater than the maximum load expected for the machine. The
BREAK 1
be set at the level where CT saturation is expected to occur.
Make the following parameter changes in EnerVista UR Setup or through the
TING GROUP 1

STATOR DIFFERENTIAL

Stage 1 of the generator unbalance element is typically used to trip the generator. In this example, the I
2
machine is 8% and the I T capability is 10. The generator nominal current is:
2
The minimum operate time of stage 1 will be set to 0.25 seconds, the maximum operating time will be 10 minutes, and the
reset time will be set to 4 minutes.
Stage 2 is typically set lower than stage 1 with a time delay to prevent nuisance alarms for external faults that are normally
cleared by system protection. For the application example, the pickup setting is:
The NEUTRL source will be chosen for this element. The settings are as follows:
GE Multilin
menu:
I primary
nom
I -------------------------------- -
= =
( )
nom pu
CT primary
×
Pickup 70% I capability
=
2
G60 Generator Management Relay
9.1.5 STATOR DIFFERENTIAL
STATOR DIFF BREAK 2
SETTINGS

9.1.6 GENERATOR UNBALANCE

6800 A
------------------ - 0.85 pu
=
8000 A
×
0.70 8% 5.6%
= =
9.1 SETTING EXAMPLE
STATOR DIFF SLOPE 1
setting
STATOR DIFF SLOPE 2
STATOR DIFF
setting should
GROUPED ELEMENTS SET-
capability of the
2
(EQ 9.5)
(EQ 9.6)
9-3
9