Assignment Of Protection Functions To Measuring Locations / Sides - Siemens SIPROTEC 4 7UT6 Series Manual

Functions
2.1 General
If the single-phase voltage input of a U4 transformer is a Uen transformer and equally assigned like the main
transformer set, then a different transformation ratio of the single-phase voltage transformer from the threep-
hase voltage transformer set can be set under address 816 Uph / Udelta. If the single-phase voltage input
at the open delta winding e-n of the voltage transformer set is connected, the voltage transformation of the
transformer is normally as follows:
[spguebersetz-spgwdlr-wlk-310702, 1, en_GB]
Factor Uph/Uen (secondary voltage) 3/√3 = √3 ≈ 1,73 must be used. For other transformation ratios, e.g. if the
residual voltage is formed by an interposed transformer set, the factor must be adapted accordingly. This
factor is of importance for the monitoring of the measured values and the scaling of the measurement and
disturbance recording signals.
If the U4 transformer set is a Uen transformer, then address 817 Uph(U4)/Udelta must be set.
817 Uph(U4)/Udelta (1.73)
2.1.4.3

Assignment of Protection Functions to Measuring Locations / Sides

Main Protection Function = Differential Protection
The main protected object, i.e. the protected object which has been selected at address 105 PROT. OBJECT
during the configuration of the protection function, is always defined by its sides, each of which can have one
or multiple measuring locations assigned to them (Section
3-phase Measuring Locations" and subsequent margin headings. Combined with the object and transformer
data according to subsection "General Power System Data", the sides define unambiguously the manner in
which to process the currents supplied by the measuring locations (CT sets) for the main protection function,
differential protection (Section
In the example shown in
S1 (high voltage side of the transformer). This ensures that the summated currents flowing through M1 and
M2 towards the protected object are evaluated as currents flowing into the transformer side S1. Likewise, the
currents flowing through M3 and M4 towards the protected object are evaluated as currents flowing into the
transformer. Where an external current flows in via M4 and out again through M3, the sum of Ι
i.e. no current flows into the protected object at that point. Nevertheless both currents are used for restraint
of the differential protection. For more details, please refer to the description of the differential protection
function (Section
By the assignment of the auxiliary measuring location X3 to side S1 of the transformer, it is defined that the 1-
phase earth fault current measured at X3 flows into the starpoint of the high-voltage winding, (Section
2.1.4 Power System Data
As the topology thus provides for the differential protection a full description of the protected object with all
its sides and measuring locations, no further information is required for this function. There are, however,
various possibilities to enter information for the other protection functions.
Restricted Earth Fault Protection
Normally, the restricted earth fault protection (Section
side of the main protected object, namely the side with the earthed starpoint. In the example shown in
Figure 2-2, this would be the side S1; therefore, address 413 REF PROT. AT would be set to Side 1. The 3-
phase measuring locations M1 and M2 have been assigned to this side during the definition of the topology.
Therefore, the sum of the currents Ι
By the assignment of the auxiliary measuring location X3 to side S1 of the transformer, it is defined that the 1-
phase earth fault current measured at X3 flows into the starpoint of the higher voltage winding, (Section
2.1.4 Power System Data
iary 1- phase Measuring Locations").
If the main protected object is an auto-transformer, the restricted earth fault protection must use the currents
of both power supply circuits of the auto-connected winding, since it cannot be determined which portion of
the earth fault current from the earthing electrode goes to the full winding and which to the tap. In
68
2.2 Differential
Figure 2-2, the 3-phase measuring locations M1 and M2 have been assigned to side
2.2 Differential Protection1).
1, under margin heading "Assignment of Auxiliary 1- phase Measuring Locations").
+ Ι is considered to be flowing into side S1 of the transformer.
M1 M2
1, "Topology of the Protected Object" under margin heading "Assignment of Auxil-
2.1.4 Power System Data 1
Protection1).
2.3 Restricted Earth Fault
under "Assignment of
+ Ι
M3 M4
Protection) is assigned to one
Figure 2-6
SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016
= 0,