Siemens SIPROTEC 7UT613 series Manual page 46

2 Functions
Terminology
46
The large variety of connection facilities of the device requires to create an exact
image of the topology of the protected object. The device must be informed in which
way the measured quantities derived from the measured value inputs of the device
have to be processed by the different protection functions.
The topology of the protected object comprises the totality of all information: how the
protected object (or several objects) is arranged, which current transformer sets
supply the currents flowing into the protected object(s), and which voltages (if avail-
able) are measured at which location of the protected object. Thus, the result of the
topological consideration is a complete replica of the protected object(s) with all avail-
able measuring locations. It will be decided at a later stage which measured quantities
should be used by which protection functions (section 2.1.6).
Distinction must be made between the Main Protected Object and other protected ob-
jects. The main protected object is that to which the main protection function, i.e. the
differential protection, is applied. This is the power transformer, generator, motor, etc.
as stated under address 105 PROT. OBJECT.
The main protected object has 2 or more sides. The sides of a power transformer are
the winding terminals, a generator or motor is terminated by the terminal side and the
starpoint side. In case of combined objects like generators and transformers in unit
connection the sides are the exterior terminals. The expression „side" is applied exclu-
sively to the main protected object.
The currents flowing into the protected object are taken from the measuring locations.
These are represented by the current transformers which limit the protected zone.
They may be or may not be identical with the sides. Differences between measure-
ment locations and sides arise, for example, if a power transformer winding (= 1 side)
is fed from 2 galvanically connected lead wires via 2 sets of current transformers (mea-
suring locations).
The measuring locations which feed a side of the main protected object are the as-
signed measuring locations. If the device provides more 3-phase current measuring
inputs than are needed for the allocation to the sides of the main protected object, the
remaining measuring points are called non-assigned measuring points. These can be
used for other protection, supervision, and measuring purposes which process
3-phase currents, e.g. restricted earth fault protection, time overcurrent protection, un-
balanced load protection, overload protection, or simply for display of measured
values. The non-assigned measuring points thus detect currents of a further protected
object.
Depending on the device version, one to four single-phase auxiliary current inputs for
auxiliary transformers. These can be used for processing of 1-phase currents, e.g. the
earth current between a winding starpoint and earth, or the leakage current between
a transformer tank and earth. They can also be assigned to the main protected object
or can be non-assigned. If they are assigned to a side of the main protected object,
they can be processed by the differential protection (example: inclusion of the star-
point current in the differential current). The currents of the non-assigned auxiliary
inputs can be processed by other protection functions (example: detection of a tank
leakage current by the single-phase overcurrent protection, or they can also be com-
bined with other non-assigned 3-phase measuring points (example: restricted earth
fault protection on a protected object other than the main protected object).
Figure 2-2 illustrates the terminology by an example. Note that the example is not
practicable in this arrangement as it contains more connections than possible; it
serves only for clarification of the terminology.
7UT613/63x Manual
C53000-G1176-C160-2