GE Multilin g60, Instruction Manual

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9-4 G60 Generator Protection System GE Multilin
9.1 SETTING EXAMPLE 9 APPLICATION OF SETTINGS
9
9.1.7 LOSS OF EXCITATION
For the example system, we have the following values:
(EQ 9.7)
(EQ 9.8)
(EQ 9.9)
(EQ 9.10)
(EQ 9.11)
(EQ 9.12)
(EQ 9.13)
(EQ 9.14)
The voltage supervision setting will be determined by a system study and may be disabled on either element if required. VT
fuse failure should supervise this element.
The choice of source is not critical for this application. The NEUTRL source is chosen for the following setting changes.
Make the following changes in EnerVista UR Setup or through the
SETTINGS

GROUPED ELEMENTS

SETTING GROUP
1

LOSS OF EXCITATION
menu:
9.1.8 REVERSE POWER
The reverse power element should be set at ½ the rated motoring power. The pickup is calculated as follows:
(EQ 9.15)
For the example system:
If the example system has delta-connected VTs instead of wye-connected VTs, and say the VT secondary setting is set to
115 V instead of 66 V, then the setting value of S
min
is calculated as follows:
(EQ 9.16)
Z
b sec ( )
base kV
2
base MVA
---------------------------
CT ratio
VT ratio
---------------------
×
18 kV ( )
2
211.765 MVA
------------------------------------
1600
157.5
---------------
× 15.54 Ω
= = =
X
d
′
(sec) X
d
′
Z
b
(sec)
×
0.216 15.54
Ω ×
3.36
Ω
= = =
X
d
sec ( ) X
d
Z
b
sec ( ) × 1.967 15.54 Ω × 30.57 Ω
= = =
CENTER 1
Z
b
sec ( ) X
d
′ (sec)
+
2
-------------------------------------------------
15.54
Ω
3.36
Ω
+
2
------------------------------------------- 9.45 Ω
= = =
RADIUS 1
Z
b
sec ( )
2
--------------------
15.54 Ω
2
----------------------
7.77
Ω
= = =
PICKUP DELAY 1 0.06 seconds
=
CENTER 2
X
d
sec
( )
X
d
′
(sec)
+
2
-------------------------------------------------
30.57 Ω 3.36 Ω
+
2
-------------------------------------------
16.97
Ω
= = =
RADIUS 2
X
d
sec
( )
2
---------------------
30.57
Ω
2
----------------------
15.28
Ω
= = =
S
min
1
2
---
Rated Motoring Power (primary watts)
3 Phase CT Primary Phase VT Ratio Phase VT Secondary × × ×
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ×
=
S
min
1
2
---
22 10
6
×
W
3 8000 A 157.5
×
66 V
× ×
--------------------------------------------------------------------- ×
0.044 pu
= =
S
min
1
2
---
22 10
6
×
W
3 8000 A 157.5 × 115 V × ×
------------------------------------------------------------------------ × 0.0253 pu
= =