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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
temperature 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
overhead lines), one of the maximum settings should be chosen at any rate.
Settings
2.7.3
The table indicates region-specific presettings. Column C (configuration) indicates the corresponding secon-
dary nominal current of the current transformer.
Addr.
Parameter
4201
FCT 49
4202
49 K-FACTOR
4203
TIME CONSTANT
4204
49 Θ ALARM
4205
I ALARM
4206
CALC. METHOD
Information List
2.7.4
No.
Information
1503
>BLOCK 49 O/L
1511
49 O / L OFF
1512
49 O/L BLOCK
1513
49 O/L ACTIVE
1515
49 O/L I Alarm
1516
49 O/L Θ Alarm
1517
49 Winding O/L
1521
49 Th O/L TRIP
SIPROTEC 4, 7SD80, Manual
E50417-G1100-C474-A2, Edition 02.2018
C
Setting Options
OFF
ON
Alarm Only
0.10 .. 4.00
1.0 .. 999.9 min
50 .. 100 %
1A
0.10 .. 4.00 A
5A
0.50 .. 20.00 A
Θ max
Average Θ
Θ from Imax
Type of
Comments
Informa-
tion
SP
>BLOCK 49 Overload Protection
OUT
49 Overload Protection is OFF
OUT
49 Overload Protection is BLOCKED
OUT
49 Overload Protection is ACTIVE
OUT
49 Overload Current Alarm (I alarm)
OUT
49 Overload Alarm! Near Thermal Trip
OUT
49 Winding Overload
OUT
49 Thermal Overload TRIP
2.7 Thermal Overload Protection 49
Default Setting
Comments
OFF
49 Thermal overload
protection
1.10
49 K-Factor
100.0 min
Time Constant
90 %
49 Thermal Alarm Stage
1.00 A
Current Overload Alarm
Setpoint
5.00 A
Θ max
Method of Acquiring
Temperature
Functions
107
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