GE Multilin g60, Instruction Manual

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GE Multilin G60 Generator Protection System 9-5
9 APPLICATION OF SETTINGS 9.1 SETTING EXAMPLE
9
To prevent maloperation for power swings the element is typically time delayed by 20 to 30 seconds. For sequential tripping
applications the time delay will be 2 to 3 seconds. The element may be blocked when the generator is offline. The line
source will be used for this application. Make the following changes in EnerVista UR Setup or through the
SETTINGS

GROUPED ELEMENTS

SETTING GROUP 1

SENSITIVE DIRECTIONAL POWER

DIRECTIONAL POWER 1
menu:
Sequential tripping logic can be implemented in FlexLogic as follows:
Figure 9–2: SEQUENTIAL TRIPPING FLEXLOGIC
9.1.9 SYSTEM BACKUP OVERCURRENT
System backup protection is implemented using a phase time overcurrent element with voltage restraint enabled. The
NEUTRL source will be chosen for this element. The pickup of this element should be set at a safe margin above the max-
imum load expected on the machine.
(EQ 9.17)
The selection of all standard curves (and FlexCurves™) is allowed for easy coordination with system relaying. For the
example system, an IEEE extremely inverse curve will be used and a setting will be chosen such that the operate time for a
three phase fault on the high side of the transformer is 0.75 seconds. For simplicity, the power system contribution is not
considered.
(EQ 9.18)
(EQ 9.19)
(EQ 9.20)
(EQ 9.21)
(EQ 9.22)
56
57
54
55
AND(2)
= SEQ TRIP (VO9)
DIR POWER 1 STG2 OP
INLET VALVE OFF(H7C)
AND(2)
= SEQ TRIP (VO9)
830731A2.CDR
PICKUP 1.5
Generator Nominal Current
CT Primary
------------------------------------------------------------------------ × 1.5
6800
8000
------------- × 1.275 pu
= = =
Transformer Impedance 0.10
211.765
200
--------------------- ×
0.106 pu on machine base
= =
Impedance to Fault 0.216 0.106
+
0.322 pu
= =
Fault Current
V
X
----
1
0.322
---------------
6800
8000
------------- × 2.64 pu
= = =
Fault Voltage Nominal Voltage
Transformer Impedance
Total Impedance
---------------------------------------------------------------- ×
18 kV
10.6
32.2
----------- ×
5.93 kV
= = =
Pickup Reduction
Fault Voltage
Generator Nominal Voltage
------------------------------------------------------------------------
5.93 kV
18 kV
-------------------- 0.329
= = =