Schweitzer Engineering Laboratories SEL-700G Series, Инструкция по эксплуатации

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4.64
SEL-700G Relay Instruction Manual Date Code 20170814
Protection and Logic Functions
Group Settings (SET Command)
Figure 4.35 Negative-Sequence Time-Overcurrent Operating Characteristic
Thermal Overload Elements
The SEL-700G thermal element provides generator overload protection based
on the thermal model described in IEC standard 60255-8. If you have the RTD
option, you can bias the model by ambient temperature.
The relay operates a thermal model with a trip value defined by the relay
settings and a present heat estimate that varies with time and changing
generator current. Figure 4.36 and Table 4.12 show a simplified model and
available settings, respectively. The relay expresses the present generator
thermal estimate as a % Thermal Capacity Used (TCU). The thermal element
asserts bit 49A when TCU reaches alarm level setting 49TAP and asserts bit
49T when the TCU reaches 100 percent. The relay uses the dropout level for
bit 49A as 90 percent of the pickup to prevent chattering. You can see the
present thermal capacity values by using the relay front-panel Meter >
Thermal function or the serial port METER T command.
10000
I2 (percent of INOM)
0.01
0.1
1
10
100
1000
100
75
50
40
30
20
10
5
2
46Q2K =
46Q2P minimum = 2.0%
46Q2T Oper
ating Time
(s
ec
onds
)
10000% 1000% 100% 10% 1%
t
op
46Q2K
I2
INOM
-----------------
 
 
2
------------------------- seconds =