2 Functions
220
7UT613/63x Manual
C53000-G1176-C160-2
2.9
Thermal Overload Protection
The thermal overload protection prevents damage to the protected object caused by
thermal overloading, particularly in case of transformers, rotating machines, power re-
actors and cables. This protection is not applicable to single-phase busbar protection.
It can be assigned to any of the sides of the main protected object, however, not to a
non-assigned measuring point.
2.9.1
General
Three methods of overload detection are available in 7UT613/63x:
• Overload calculation using a thermal replica according to IEC 60255-8, without
ambient temperature influence
• Overload calculation using a thermal replica according to IEC 60255-8, with
ambient temperature influence
• Calculation of the hot-spot temperature and determination of the ageing rate ac-
cording to IEC 60354.
You may select one of these three methods. The first one is characterised by easy
handling and setting; it calculates the overtemperature caused by current heat losses.
For the second one the ambient or coolant temperature is taken into consideration; it
calculates the total temperature. It is required that the decisive coolant temperature is
signalled to the device via a connected RTD box.
The third needs some knowledge about the protected object and its thermal charac-
teristics and the input of the cooling medium temperature.
7UT613/63xis equipped with two breaker failure protection functions that can be used
independent of each other and for different locations of the protective object. One can
also work with different starting criteria. The assignment of the protective functions to
the protected object are performed as described in section „Assignment of Protection
Functions to Measuring Locations/Sides“.
2.9.2
Overload Protection Using a Thermal Replica
Principle
The overload protection of 7UT613/63x can be assigned to one of the sides of the
main protected object (selectable). Since the cause of overload is normally outside the
protected, the overload current is a through-flow current.
The unit computes the temperature rise according to a thermal single-body model as
per the following thermal differential equation
T
actual valid temperature rise referred to the final temperature rise at maximum permis-
sible current of the assigned side of the protected object k ·
I
N Obj
τ
th
thermal time constant for the heating
k
k-factor which states the maximum permissible continuous current, referred to the rated
current of the assigned side of the protected object
I
currently valid RMS current of the assigned side of the protected object
I
N Obj
rated current of the assigned side of the protected object
Summary of Contents for SIPROTEC 7UT613 series
Page 16: ...Contents 16 7UT613 63x Manual C53000 G1176 C160 2 Literature 631 Glossary 623 Index 633 ...
Page 30: ...1 Introduction 30 7UT613 63x Manual C53000 G1176 C160 2 ...
Page 506: ...A Appendix 506 7UT613 63x Manual C53000 G1176 C160 2 7UT633 D E ...
Page 508: ...A Appendix 508 7UT613 63x Manual C53000 G1176 C160 2 7UT633 P Q ...
Page 510: ...A Appendix 510 7UT613 63x Manual C53000 G1176 C160 2 7UT635 D E ...
Page 512: ...A Appendix 512 7UT613 63x Manual C53000 G1176 C160 2 7UT635 P Q ...
Page 515: ...A 2 Terminal Assignments 515 7UT613 63x Manual C53000 G1176 C160 2 7UT633 B ...
Page 517: ...A 2 Terminal Assignments 517 7UT613 63x Manual C53000 G1176 C160 2 7UT633 N ...
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Page 622: ...A Appendix 622 7UT613 63x Manual C53000 G1176 C160 2 ...
Page 632: ...Literature 632 7UT613 63x Manual C53000 G1176 C160 2 ...