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Functions
2.7 Thermal Overload Protection 49
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
115
Calculating the Overtemperature
The thermal replica is calculated individually for each phase. Address
4206
CALC. METHOD
decides whether
the highest of the three calculated temperatures (
Θ
max
) or their arithmetic average (
Average
Θ
) or the tem-
perature calculated from the phase with maximum current (
Θ
from Imax
) should be decisive for the thermal
alarm and tripping element.
Since an overload usually occurs in a balanced way, this setting is of minor importance. If unbalanced over-
loads are to be expected, however, these options lead to different results.
Averaging should only be used if a rapid thermal equilibrium is possible in the protected object, e.g. with belted
cables. If the three phases are, however, more or less thermally isolated (e.g. single conductor cables or over-
head lines), one of the maximum settings should be chosen at any rate.
2.7.3
Settings
The table indicates region-specific default settings. Column C (configuration) indicates the corresponding sec-
ondary nominal current of the current transformer.
2.7.4
Information List
Addr.
Parameter
C
Setting Options
Default Setting
Comments
4201
FCT 49
OFF
ON
Alarm Only
OFF
49 Thermal overload pro-
tection
4202
49 K-FACTOR
0.10 .. 4.00
1.10
49 K-Factor
4203
TIME CONSTANT
1.0 .. 999.9 min
100.0 min
Time Constant
4204
49
Θ
ALARM
50 .. 100 %
90 %
49 Thermal Alarm Stage
4205
I ALARM
1A
0.10 .. 4.00 A
1.00 A
Current Overload Alarm
Setpoint
5A
0.50 .. 20.00 A
5.00 A
4206
CALC. METHOD
Θ
max
Average
Θ
Θ
from Imax
Θ
max
Method of Acquiring Tem-
perature
No.
Information
Type of In-
formation
Comments
1503
>BLOCK 49 O/L
SP
>BLOCK 49 Overload Protection
1511
49 O / L OFF
OUT
49 Overload Protection is OFF
1512
49 O/L BLOCK
OUT
49 Overload Protection is BLOCKED
1513
49 O/L ACTIVE
OUT
49 Overload Protection is ACTIVE
1515
49 O/L I Alarm
OUT
49 Overload Current Alarm (I alarm)
1516
49 O/L
Θ
Alarm
OUT
49 Overload Alarm! Near Thermal Trip
1517
49 Winding O/L
OUT
49 Winding Overload
1521
49 Th O/L TRIP
OUT
49 Thermal Overload TRIP