GE M60 Instruction Manual page 353
Motor protection system
ur series
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- Instruction manual (676 pages) ,
- Communications manual (532 pages) ,
- Communications manual (526 pages)
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5 SETTINGS
•
The motor load is steady.
Variations in motor load cause spectral components that can be misinterpreted as rotor bar failure. Instantaneous
motor load values are collected alongside with data for the broken rotor bar algorithm to prevent this from happening.
The average motor load and its standard deviation are calculated. If the standard deviation is greater than its corre-
sponding setting, the data set is discarded and the broken bar algorithm is not initiated.
•
The motor current unbalance is below a corresponding setpoint.
The excessive current unbalance stresses the motor, and it may cause a false broken rotor bar detection.
It is recommended that frequency tracking be enabled to avoid possible false broken rotor bar detection results when the
system frequency drifts from the nominal frequency.
The following settings are available for the broken rotor bar detection element.
•
START OF BRB OFFSET: This setting specifies the beginning of the frequency range where the spectral component
due to a rotor bar failure will be searched. The beginning of the frequency range is defined as follows, where f
system frequency and f
start_offset
If the upper sideband is to be measured, this setting should be programmed as follows, where f
quency and s is the motor slip at full load.
For example, if the full load slip is 0.01, program this setting as follows for a 60 Hz power system.
If the lower sideband is to be measured, this setting should be programmed as follows, where f
quency and s is the motor slip at full load.
Using the same values from previous example, this value should be programmed as follows.
•
END OF BRB OFFSET: This setting specifies the end of the frequency range where the spectral component due to a
rotor bar failure will be searched. The end of the frequency range is defined as follows, where f
quency and f
is this setting
end_offset
If the upper sideband is to be measured, this setting should be programmed as follows, where f
quency and s is the motor slip at full load.
For example, if the full load slip is 0.01, program this setting as follows for a 60 Hz power system.
If the lower sideband is to be measured, this setting should be programmed as follows, where f
quency and s is the motor slip at full load.
Using the same values from previous example, this value should be programmed as follows.
GE Multilin
is this setting.
f
f
f
=
+
start
1
start_offset
(
,
f
2sf
max 0.3 min 2sf
=
–
start_offset
1
f
2sf
max 0.3 min 2sf
(
,
=
–
start_offset
1
2
×
0.01 60
×
Hz 0.8
=
f
– sf
2
max 0.3 min 2sf
(
=
–
start_offset
1
f
– sf
2
max 0.3 min 2sf
(
=
–
start_offset
1
×
×
2 0.01
60 Hz
=
–
f
f
f
=
+
end
1
end_offset
f
2sf
max 0.3 min 2sf
(
,
=
+
end_offset
1
f
2sf
max 0.3 min 2sf
(
,
=
+
end_offset
1
×
×
2 0.01 60
Hz
=
(
f
– sf
2
max 0.3 min 2sf
=
+
end_offset
1
(
f
– sf
2
max 0.3 min 2sf
=
+
end_offset
1
×
×
2
0.01 60 Hz
=
–
M60 Motor Protection System
(
,
)
)
0.4
1.0
–
1
(
0.4
,
1.0
)
)
–
1
0.40 Hz
–
=
,
(
0.4
,
1.0
)
)
–
1
,
(
0.4
,
1.0
)
)
–
1
0.8
2.00 Hz
–
=
–
(
0.4
,
1.0
)
)
–
1
(
0.4
,
1.0
)
)
–
1
0.8
2.00 Hz
+
=
,
(
,
)
)
0.4
1.0
–
1
,
(
,
)
)
0.4
1.0
–
1
0.8
0.40 Hz
+
=
–
5.7 CONTROL ELEMENTS
is the
1
(EQ 5.41)
is the system fre-
1
(EQ 5.42)
(EQ 5.43)
is the system fre-
1
(EQ 5.44)
(EQ 5.45)
is the system fre-
1
(EQ 5.46)
is the system fre-
1
(EQ 5.47)
(EQ 5.48)
is the system fre-
1
(EQ 5.49)
(EQ 5.50)
5-215
5
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