Siemens Siprotec 7UM611 Manual page 81

Figure 2-23
The primary setting values can be read out directly from the diagram. The related
values must be converted for the protection setting. The same conversion formula can
be used if the protection setting is performed with the predefined synchronous direct
reactance.
with
x
x
I
U
U
I
Instead of 1/x
current at no-load excitation).
7UM61 Manual
C53000-G1176-C127-3
Capability Curve of a Salient-Pole Generator, Indicated per Unit
related synchronous direct reactance, secondary,
dsec
related synchronous direct reactance of the machine,
d mach
Nominal Current of the Machine
NMach
Nominal Voltage of the Machine
NMach
Primary Nominal Voltage of the voltage transformers
N VT. prim
Nominal primary CT current
N CT prim
the approximate value I
d mach
2.11 Underexcitation (Loss-of-Field) Protection (ANSI 40)
/I can be used (with I
K0 N
= short-circuit
K0
81