Siemens SIPROTEC 7UT613 series Manual page 64

2 Functions
64
If the voltage transformers represented as Ua do not exist in your system, you can, for
instance, use the voltages at Measuring loc.2 (represented as Ub), as they are
electrically identical (assuming that the circuit breaker is closed). The device then
assigns the voltage automatically to side 1 and calculates the power of the side from
this voltage and the current of side S1, which is the sum of the currents from the mea-
suring locations M1 and M2.
If no voltages are connected, set Not connected.
If the overflux protection function is used, you must choose (and connect) a voltage
that is suitable for overflux protection. For transformers it must be a non-regulated
side, since a proportional relationship between the quotient U/f and the iron core in-
duction B is found only there. If, for example in figure 2-8 the winding at side 1 has a
voltage controller, Side 2 must be selected.
For the power protection functions it is important that the voltages are measured at
such locations where the currents are flowing from which the power will be calculated.
If, for example, the power is relevant that is flowing from the high-voltage side (side
S1) into the transformer, as shown in figure 2-8, the assignment is set at address
261 VT SET = Side 1. At the measuring locations M1 and M2 the flowing currents
are multiplied by the voltage at Ua, in order to obtain the power.
In case of reverse power protection for a generator, the currents are usually measured
in the starpoint leads and the voltages at the terminal side (figure 2-9). It is also advis-
able here to not to assign the voltage to measuring location M2 or to side S2, but to
measuring location M1 or to side S1. For the power calculation the voltages at U with
currents at M1 are taken into consideration. It is thus ensured that the active power
supply of the generator from the network is evaluated as reverse power.
Figure 2-9 Power measurement at generator
If you have the choice to assign a side or a measuring location to the main protected
object as shown in figure 2-9 (S1 is identical to M1), such assignment of the side is
preferable, because the power can be set later directly in the (mostly known) reference
values. As the nominal data of the main protected object are known to the device, no
conversion of reference values to secondary values will be required.
The under- and overvoltage protection and the frequency protection also use the volt-
ages connected to the device. Select the side or measuring location here, which is
electrically connected to the voltage transformer set.
Should the voltages not be required for the protection functions, select the voltages
that must be indicated or transferred as operational measured values during opera-
tion, or on the basis of which you wish to calculate the power.
For the 1-phase voltage measurement input U4, likewise a side or measuring location
can be selected at address 262 VT U4 - irrespective of the assignment of the 3-phase
voltage inputs. This measuring input is frequently used for the displacement voltage,
measured at the e-n windings of the voltage transformer set, but you can also use it
for detection of any other measured voltage. In this case set VT U4 = conn/not
assig. (connected, but not assigned). If no voltage is needed at the 1-phase voltage
input, set Not connected (not connected).
7UT613/63x Manual
C53000-G1176-C160-2