Siemens SIPROTEC 7UT613 series Manual page 80

2 Functions
Further 3-phase
Protection Func-
tions
80
Since the assignment of the 3-phase measuring locations and of the auxiliary measur-
ing location is also defined by the topology, you only need to set auto-connected
for the restricted earth fault protection REF PROT. AT. This is also true if the auto-
connected winding has more than one tap.
But the restricted earth fault protection can also act upon an object other than the main
protected object. In Figure 2-3 the main protected object is a three-winding transform-
er with the sides S1, S2 and S3. The 3-phase measuring location M5, on the other
hand, belongs to the neutral reactor. You have now the option to use the restricted
earth fault protection for this reactor. Since for this further protected object no sides
are defined, you can assign here the restricted earth fault protection to the 3-phase
measuring location M5, which is not assigned to the main protected object: set
address 413 REF PROT. AT to n.assigMeasLoc5.
By the assignment of the auxiliary measuring location X4 to the 3-phase measuring
location M5, it is defined that the 1-phase earth fault current measured at X4 belongs
to the neutral reactor connected to M5 (subsection „Topology of the Protected Object"
under margin heading „Assignment of Auxiliary 1-phase Measuring Locations").
7UT613/63x provides a second earth fault differential protection. A earth fault differ-
ential protection for both of the windings can be implemented in a YNyn transformer,
for example, that is earthed at both starpoints. Or use the first earth fault differential
protection for an earthed transformer winding and the second for a further protective
object, e.g. a neutral reactor. Set address 414 REF PROT. 2 AT in accordance with
the aspects as for the first earth fault differential protection.
A reminder: the single-phase power transformer is treated like a three-phase power
transformer (without phase L2). Therefore, the three-phase protection functions apply
also for this (except the overcurrent protection for zero sequence current and asym-
metrical load protection).
These further protection functions can operate on the main protected object or on a
further protected object. The possibilities depend on the definitions made in the topol-
ogy.
For the main protection object, you normally choose one side for which the protection
function will be effective. If in the example shown in Figure 2-2 you want to use the
time overcurrent protection for phase currents (Section 2.4.1) as a backup protection
on the high-voltage side, you set address 420 DMT/IDMT Ph AT to Side 1. The
phase overcurrent protection then acquires the sum of the currents flowing through the
measuring locations M1 and M2 (for each phase) towards the transformer.
You can also set the phase overcurrent protection to be effective for one single mea-
suring location of the main protected object. If in the same example you want to use
the overcurrent protection as a protection for the auxiliaries system circuit, you set
address 420 DMT/IDMT Ph AT to Measuring loc.3.
Finally, you can also set the overcurrent protection to be effective for another protec-
tion object, i.e. assign it to a 3-phase measuring location which is not assigned to the
main protection object. To do so, you select that measuring location. In the example
shown in Figure 2-2, you can use the overcurrent protection as a protection for the
cable feeder by setting address 420 DMT/IDMT Ph AT to Measuring loc.5.
7UT613/63x Manual
C53000-G1176-C160-2