2 Functions
104
7UT613/63x Manual
C53000-G1176-C160-2
2.2
Differential Protection
The differential protection represents the main protection feature of the device. It is
based on current comparison under consideration of the transformation ratio of the
transformer.7UT613/63x is suitable for unit protection of transformers, generators,
motors, reactors, short lines, and (under observance of the available number of ana-
logue current inputs) and (under observance of the available number of analogue
current inputs) busbars. Protection of generator/transformer units, transformer/wind-
ing combinations or transformer/starpoint former, can also be realised. 7UT613 and
7UT633 allow up to 3, 7UT635 allows up to 5 three-phase measuring locations.
7UT613/63x can also be used as a single-phase device. In this case, 7UT613 and
7UT633 allow up to 9, 7UT635 allows up to 12 measuring locations, e.g. currents from
a busbar with up to 9 or 12 feeders.
The protected zone is selectively limited by the CTs at its ends.
2.2.1
Functional Description of the Differential Protection
Processing of the measured values depends on the way the differential protection is
used. This section discusses first the differential protection function in general, regard-
less of the type of protected object. A single-phase system is referred to. Particulars
with regard to the individual protected objects follow thereafter.
Basic Principle with
Two Sides
Differential protection is based on current comparison. It makes use of the fact that a
protected object carries always the same current i (dashed line in 2-17 below) at its
two sides in healthy operation. This current flows into one side of the considered zone
and leaves it again on the other side. A difference in currents is a clear indication of a
fault within this section. If the actual current transformation ratio is the same, the sec-
ondary windings of the current transformers
CT1
and
CT2
at the sides of the protected
object can be connected to form a closed electric circuit with a secondary current
I
; a
measuring element
M
, which is connected to the electrical balance point, remains at
zero current in healthy operation.
Figure 2-17
Basic principle of differential protection for two sides (single-phase illustration)
When a fault occurs in the zone limited by the transformers, a current i
1
+ i
2
, which is
proportional to the fault currents
I
1
+
I
2
flowing in from both sides is fed to the measur-
ing element. As a result, the simple circuit shown in Figure 2-17 ensures a reliable trip-
ping of the protection if the fault current flowing into the protected zone during a fault
is high enough for the measuring element
M
to respond.
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 ...
Page 519: ...A 2 Terminal Assignments 519 7UT613 63x Manual C53000 G1176 C160 2 7UT635 B ...
Page 521: ...A 2 Terminal Assignments 521 7UT613 63x Manual C53000 G1176 C160 2 7UT635 N ...
Page 622: ...A Appendix 622 7UT613 63x Manual C53000 G1176 C160 2 ...
Page 632: ...Literature 632 7UT613 63x Manual C53000 G1176 C160 2 ...