1MAC050144-MB C
Section 4
Protection functions
615 series ANSI
293
Technical Manual
4.5
Thermal protection
4.5.1
Three-phase thermal protection for feeders, cables and
distribution transformers, 49F
4.5.1.1
Identification
4.5.1.2
Function block
Figure 140:
Function block
4.5.1.3
Functionality
The increased utilization of power systems closer to the thermal limits has generated a
need for a thermal overload function for power lines as well.
A thermal overload is in some cases not detected by other protection functions, and the
introduction of the thermal overload function 49F allows the protected circuit to operate
closer to the thermal limits.
An alarm pickup gives an early warning to allow operators to take action before the line
trips. The early warning is based on the three-phase current measuring function using a
thermal model with first order thermal loss with the settable time constant. If the
temperature rise continues the function will operate based on the thermal model of the line.
Re-energizing of the line after a thermal overload operation can be inhibited for a time to
allow the line to cool. The time for the line to cool is estimated by the thermal model.
4.5.1.4
Operation principle
The function can be enabled and disabled with the
Operation
setting. The corresponding
parameter values are Enable and Disable.
The operation of three-phase thermal protection can be described by using a module
diagram. All the blocks in the diagram are explained in the next sections.
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Three-phase thermal overload protection
for overhead lines and cables
T1PTTR
3lth>
49F
49F
I_C
ENA_MULT
BLK_OPR
TRIP
ALARM
BLK_CLOSE
I_B
I_A
PICKUP
AMB_TEMP
Summary of Contents for 615 Series ANSI
Page 1: ...Relion Protection and Control 615 series ANSI Technical Manual ...
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Page 29: ...1MAC050144 MB C Section 615 series ANSI 22 Technical Manual ...
Page 389: ...Section 4 1MAC050144 MB C Protection functions 382 615 series ANSI Technical Manual ...
Page 485: ...Section 6 1MAC050144 MB C Supervision functions 478 615 series ANSI Technical Manual ...
Page 635: ...Section 10 1MAC050144 MB C Other functions 628 615 series ANSI Technical Manual ...
Page 711: ...Section 16 1MAC050144 MB C Glossary 704 615 series ANSI Technical Manual ...
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