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
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