Siemens Siprotec 7UM611 Manual page 277

Calculation of Pro- Coupling capacitance C
tected Zone R
Figure 3-17
Equivalent circuit and vector diagram Since the reactance of the coupling capacitance
is much larger than the referred resistance of the loading resistor RB', U
can be set (see also vector diagram Figure 3-17), where U
placement voltage with a full displacement of the network voltage starpoint. The fol-
lowing applies:
With the voltage transformation ratio TR of the earthing transformer:
we obtain:
7UM61 Manual
C53000-G1176-C127-3
and loading resistor R
C
is the resistance R referred to the machine terminal circuit.
B B
Equivalent Diagram and Vector Diagram
3.3 Commissioning
represent a voltage divider, whereby
B
/√3 is the neutral dis-
NO
≈ U
/√3
C NO
277