2 Functions
204
7UT613/63x Manual
C53000-G1176-C160-2
The required short-term power of the resistor is derived from the knee-point voltage
and the resistance:
As this power only appears during earth faults for a short period of time, the rated
power can be smaller by approx. factor 5.
The varistor (see figure below) must be dimensioned in such manner that it remains
high-ohmic up to the knee-point voltage, e.g.
approx. 100 V for 5-A CT,
approx. 500 V for 1-A CT.
Figure 2-91
Connection scheme for restricted earth fault protection according to the high-im-
pedance principle
The pickup value (0.1 A or 0.05 A in the example) is set in address
2706
1Phase I>
.
The
I
>> stage is not required (address
2703
1Phase I>>
=
∞
).
The trip command can be delayed under address
2707
T 1Phase I>
. This time
delay is usually set to
0
.
If a higher number of current transformers is connected in parallel, e.g. when using as
busbar protection with several feeders, the magnetising currents of the transformers
connected in parallel cannot be neglected anymore. In this case, the sum total of the
magnetising currents at half knee-point voltage (corresponding to the setting value)
has to be established. These magnetising currents reduce the current through the re-
sistor R. The actual pickup value thus increases accordingly.
Use as Tank
Leakage Protection
If the single-phase time overcurrent protection is used as tank leakage protection, only
the pickup value for the respective 1-phase current input is set on 7UT613/63x.
The tank leakage protection is a highly sensitive overcurrent protection which detects
the leakage current between the isolated transformer tank and earth. Its sensitivity is
set in address
2706
1Phase I>
. Stage
I
>> is not used (address
2703
1Phase I>>
=
∞
).
The trip command can be delayed in address
2707
T 1Phase I>
. Normally, this
delay time is set to
0
.
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 ...
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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 ...