GE 489 - Manual (Page 118)

4-68 489 Generator Management Relay GE Multilin
4.10 S9 THERMAL MODEL 4 SETPOINTS
4
It should be noted that the RTD bias feature alone cannot create a trip. If the RTD bias feature forces the thermal capacity
used to 100%, the machine current must be above the over-load pickup before an overload trip occurs. Presumably, the
machine would trip on stator RTD temperature at that time.
Figure 4–18: RTD BIAS CURVE
4.10.3 THERMAL ELEMENTS
SETPOINTS ÖØ S9 THERMAL MODEL ÖØ THERMAL ELEMENTS
Once the thermal model is setup, an alarm and/or trip element can be enabled. If the generator has been offline for a long
period of time, it will be at ambient temperature and thermal capacity used should be zero. If the generator is in overload,
once the thermal capacity used reaches 100%, a trip will occur. The thermal model trip will remain active until a lockout time
has expired. The lockout time will be based on the reduction of thermal capacity from 100% used to 15% used. This reduc-
tion will occur at a rate defined by the stopped cooling time constant. The thermal capacity used alarm may be used as a
warning indication of an impending overload trip.
„ THERMAL ELEMENTS
„ [ENTER] for more
THERMAL MODEL
ALARM: Off
Range: Off, Latched, Unlatched
ASSIGN ALARM
RELAYS (2-5): ---5
Range: Any combination of Relays 2 to 5
THERMAL ALARM
LEVEL: 75% Used
Range: 10 to 100% Used in steps of 1
THERMAL MODEL
ALARM EVENTS: Off
Range: On, Off
THERMAL MODEL
TRIP: Off
Range: Off, Latched, Unlatched
ASSIGN TRIP
RELAYS (1-4): 1---
Range: Any combination of Relays 1 to 4
808721A1.CDR
Maximum Stator RTD Temperature
0
20
40
60
80
100
–50 0 50 100 150 200 250
RTD Bias Maximum
RTD Bias Center Point
RTD Bias Minimum
Hot/Cold = 0.85
Rated Temperature=130°C
Insulation Rating=155°C
RTD
T
h
er
m
a
l
Capa
ci
ty
U
s
ed
ENTER
ESCAPE
р
р
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE