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7UM62 Manual
C53000-G1176-C149-3
Note:
The generator diagram can be visualized in more than one way. Figure 2-51 shows a
form that is quite common at Siemens Power Generation, with a rotation of 90° and
mirroring at the active power axis.
The 7UM62 underexcitation protection provides three independent characteristics
which can be freely combined. As illustrated in Figure 2-52, it is, for example, possible
to model the static machine stability characteristic by means of two partial
characteristics with the same time delays (T CHAR. 1 = T CHAR. 2). The partial
characteristics are distinguished by the corresponding distance from the zero point (1/
xd CHAR. 1) and (1/xd CHAR. 2) the corresponding inclination angle
If the resulting characteristic (1/xd CHAR.1)/
Figure 2-52 to the left side), a delayed warning (e.g. by 10 s) or a trip signal are
transmitted. The delay is necessary to ensure that the voltage regulator is given
enough time to increase the excitation voltage.
Charact. 2
Charact. 3
α
3
B [p.u.]
where
⁄
P S
----------------------- -
G [p.u.]
=
(
⁄
U U
⁄
–Q S
B [p.u.]
----------------------- -
=
(
⁄
U U
Figure 2-52
Stator Criterion: Pick–Up Characteristic in Admittance Diagram
A further characteristic (1/xd CHAR.3 /
characteristic of the synchronous machine. Since stable operation is impossible if this
characteristic is exceeded, immediate tripping is required in this case (T CHAR 3 time
stage).
Underexcitation (Loss-of-Field) Protection (ANSI 40)
α
1; (1/xd CHAR.2)/
G [p.u.]
Characteristic 1
E/U
I/U
α
1
α
δ
2
1/xd
CHAR.1
1/xd
CHAR.2
1/xd
CHAR.3
N
Conductance per unit
2
)
N
N
Susceptance per unit
2
)
N
α
can be matched to the dynamic stability
3
α
α
1 and
2.
α
is exceed (in
2
107
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