GE G60 UR Series, Instruction Manual

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GE Multilin G60 Generator Protection System 10-7
10 APPLICATION OF SETTINGS 10.1 SETTING EXAMPLE
10
The zone 3 reach will be set at 120% of the generator transient reactance. The time delay of this element should be com-
pared to the generator decrement curve to verify the adequacy of this setting.
(EQ 10.27)
(EQ 10.28)
An mho shape has been chosen for this example. Therefore, the quadrilateral settings are left at their default values. Make
the following changes in EnerVista UR Setup or through the
SETTINGS
ÖØ
GROUPED ELEMENTS
ÖØ
SETTING GROUP 1
ÖØ
DISTANCE
Ö
PHASE DISTANCE Z1(3)
menus:
10.1.11 STATOR GROUND FAULT
a) AUXILIARY OVERVOLTAGE
Stator ground fault protection is implemented with an overvoltage element connected at the generator neutral resistor. The
auxiliary overvoltage element will be used in this example. The auxiliary voltage input has previously been assigned to the
NEUTRL source. In this example the element will be set to protect 97% of the stator against ground faults.
(EQ 10.29)
Generator impedance X
d
V
L
2
MVA
G
----------------
×
j 1.967
18
( )
2
211
--------------
×
j 3.01 primary ohms
= = =
Zone 3 reach 1.2 Generator impedance
CT ratio
VT ratio
---------------------
× ×
=
1.2 j 3.01
×
1600
157.5
---------------
×
= j 36.68 secondary ohms =
PICKUP 0.03
Nominal Phase Ground Voltage
–
Ground VT Primary
----------------------------------------------------------------------------------------
×
0.03
18000 3
⁄
12000
----------------------------
×
0.026 pu = = =