GE G60 UR Series, Instruction Manual

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GE Multilin G60 Generator Protection System 10-3
10 APPLICATION OF SETTINGS 10.1 SETTING EXAMPLE
10
10.1.5 STATOR DIFFERENTIAL
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
STATOR DIFF SLOPE 1
setting to accommodate for CT errors; a setting of 10% is adequate in most instances. Set the
STATOR DIFF SLOPE 2
setting
to accommodate for errors due to CT saturation; a setting of 80% is recommended for most applications. The
STATOR DIFF
BREAK 1
setting must be greater than the maximum load expected for the machine. The
STATOR DIFF BREAK 2
setting should
be set at the level where CT saturation is expected to occur.
Make the following parameter changes in EnerVista UR Setup or through the
SETTINGS
ÖØ
GROUPED ELEMENTS
ÖØ
SET-
TING GROUP 1
ÖØ
STATOR DIFFERENTIAL
Ö
menu:
10.1.6 GENERATOR UNBALANCE
Stage 1 of the generator unbalance element is typically used to trip the generator. In this example, the I
2
capability of the
machine is 8% and the I
2
2
T capability is 10. The generator nominal current is:
(EQ 10.5)
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:
(EQ 10.6)
Source 2 will be chosen for this element. The settings are as follows:
I
nom pu
( )
I
nom
primary
CT primary
---------------------------------
6800 A
8000 A
-------------------
0.85 pu
= = =
Pickup 70% I
2
capability
×
0.70 8%
×
5.6% = = =