Time Overcurrent Protection For Earth Current; General; Definite Time, Instantaneous Overcurrent Protection (Umz) - Siemens SIPROTEC 7UT613 series Manual

2.5

Time Overcurrent Protection for Earth Current

2.5.1

General

2.5.2

Definite Time, Instantaneous Overcurrent Protection (UMZ)

7UT613/63x Manual
C53000-G1176-C160-2
The time overcurrent protection for earth current is assigned to a 1-phase measured
current input of the device. It can be used for any desired single-phase application. Its
preferred application is the detection of an earth current between the starpoint of a pro-
tective object and its earth electrode (that's why the description). The corresponding
one-phase additional measuring input has to be correctly assigned to the one-phase
current transformer of the power plant.
This protection can be used in addition to the restricted earth fault protection (Section
2.3). Then it forms the backup protection for earth faults outside the protected zone
which are not cleared there.
The time overcurrent protection for earth current provides two definite time stages (O)
and one inverse time stage (C). The latter may operate according to an IEC or an
ANSI, or a user defined characteristic.
Figure 2-77 Time overcurrent protection as backup protection for restricted earth fault pro-
tection
7UT613/63x is provided with two overcurrent functions for earth current, where each
can be used independent of each other at different locations. Assigning the different
protective functions to the one-phase measuring locations are according to Section
„Assigning the protective function to the measuring locations/sides" performed.
The definite time stages (O) for earth current are always available even if an inverse
time characteristic has been configured in the scope of functions (see Subsection
2.1.3.1).
2.5 Time Overcurrent Protection for Earth Current
179