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GE Multilin G60 Generator Protection System 9-3

9 APPLICATION OF SETTINGS 9.1 SETTING EXAMPLE

9.1.5 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  GROUPED ELEMENTS  SET-

TING GROUP 1  STATOR DIFFERENTIAL  menu:

9.1.6 GENERATOR UNBALANCE

Stage 1 of the generator unbalance element is typically used to trip the generator. In this example, the I

capability of the

machine is 8% and the I

T capability is 10. The generator nominal current is:

(EQ 9.5)

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 9.6)

Source 2 will be chosen for this element. The settings are as follows:

nom pu()

nom

primary

CT primary

---------------------------------

6800 A

8000 A

-------------------

0.85 pu===

Pickup 70% I

capability× 0.70 8%× 5.6%===

GE G60 User Manual

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