2.1 General
79
7UT613/63x Manual
C53000-G1176-C160-2
If the U4 transformer set is a Uen transformer, then address 817 Uph(U4)/Udelta
must be set.
817 Uph(U4)/Udelta (0.10-9.99 ; without 0)
2.1.4.3 Assignment of Protection Functions to Measuring Locations / Sides
Main Protection
Function = Differen-
tial 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 loca-
tions assigned to them (section 2.1.4 under „Assignment of 3-phase Measuring Loca-
tions“ and subsequent margin headings. Combined with the object and transformer
data according to subsection „General Power System Data“, the sides define unam-
biguously the manner in which to process the currents supplied by the measuring lo-
cations (CT sets) for the main protection function, differential protection (section
2.2.1).
In the example shown in Figure 2-2, the 3-phase measuring locations M1 and M2 have
been assigned to side S1 (high-voltage side of the transformer). This ensures that the
summated currents flowing through M1 and M2 towards the protected object are eval-
uated 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 I
M3
+ I
M4
= 0, 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 (sub-
section 2.2.1).
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, (subsection 2.1.4, „Topology of the Protected Object“
under margin heading „Assignment of Auxiliary 1-phase Measuring Locations“).
As the topology thus provides for the differential protection a full description of the pro-
tected object with all its sides and measuring locations, no further information is re-
quired 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 2.3) is assigned to one 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 I
M1
+ I
M2
is considered to be flowing into side S1 of the transformer.
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, (subsection 2.1.4, „Topology of the Protected Object“
under margin heading „Assignment of Auxiliary 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 Figure 2-6 the currents of
the 3-phase measuring locations M1 and M2 flow into the auto-connected winding, the
1-phase earth fault current is measured at the auxiliary measuring location X3. The 3-
phase measuring location M3 is irrelevant for the restricted earth fault protection.
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