4.65
Date Code 20170814
Instruction Manual
SEL-700G Relay
Protection and Logic Functions
Group Settings (SET Command)
Figure 4.36
Simplified Thermal Model, Generator
If the thermal model is turned off (E49T := N), the thermal model is disabled,
the output of the thermal model is blocked, and the relay reports
the % Thermal Capacity as 0, as noted in Section 5: Metering and Monitoring.
When you enable overload protection, the relay requires information about the
protected generator. Obtain the time constant information from the generator
specifications; all other settings are based on the protection practices of the
individual user. Set thermal overload level 1 to the necessary overload pickup
in per unit of INOM (see Table 4.2) and set thermal overload level 2 to the
necessary thermal capacity to trigger alarm/indication prior to an overload trip.
Use the Alternate Cooling Mode SEL
OGIC
control equation to dynamically
change the time constant for the generator cooling status. For example,
ALTCOOL := IN303 switches the time constant a system uses from GTC1 to
GTC2 when IN303 asserts, indicating a cooling system failure.
When the relay is monitoring one or more RTDs in the generator windings and
an ambient temperature RTD, you can bias the thermal model by ambient
temperature when ETHMBIAS := Y. The relay uses the ambient temperature
above 40°C and the winding RTD trip temperature setting to calculate the
overload RTD bias.
Figure 4.37 shows the generator overload curve for specified settings and
preload current. Use the following equation to calculate trip time or to plot the
curve for any settings you want.
Table 4.12
Thermal Overload Settings
Setting Prompt
Setting Range
Setting Name :=
Factory Default
THERM OVERLD EN
Y, N
E49T := N
THERM OL TRIP PU
0.30–2.50 pu
49TTP := 1.10
TIME CONSTANT1
1–1000 min
GTC1 := 10
TIME CONSTANT2
OFF, 1–1000 min
GTC2 := OFF
ALT COOLING MODE
SEL
OGIC
ALTCOOL := 0
TCU ALARM PU
OFF, 50–99 %
49TAP := 85
OL RTD BIASING?
Y, N
ETHMBIAS := N
I1 = Positive-sequence generator current, amps
I2 = Negative-sequence generator current, amps
GTC = 60 • GTC1 if Relay Word bit ALTCOOL = 0
GTC = 60 • GTC2 if Relay Word bit ALTCOOL = 1
49TTP, INOM, GTC1, GTC2 = Relay settings
%TCU = (U
Gen
/ TV
Gen
) • 100
TV
Gen
= 49TTP
2
(I1
2
+ I2
2
)
INOM
2
U
Gen
GTC
R = 1
49T
Relay
Word
Bit
Summary of Contents for SEL-700G Series
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