Ice NP900 Series, Инструкция по применению

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Application Guide - NP900 Series 164 (504
)
A996A
Table 3.2.15.1-113 Analogic magnitudes used by the VJP function.
Signal Description Time base
U
1
L-L Measured Line-to-Line voltage U
1
/V 5 ms
U
2
L-L Measured Line-to-Line voltage U
2
/V 5 ms
U
3
L-L Measured Line-to-Line voltage U
3
/V 5 ms
U
1
L-N Measured Line-to-Neutral voltage U
1
/V 5 ms
U
2
L-N Measured Line-to-Neutral voltage U
2
/V 5 ms
U
3
L-N Measured Line-to-Neutral voltage U
3
/V 5 ms
U
4
Measured voltage U
4
/V 5 ms
Selection of the used AI channel is made with a setting parameter. In all possible input
channel variations pre-fault condition is presented with 20 ms averaged history value from
-20 ms of Alarm or Trip event.
3.2.15.2 P
ICK
-
UP CHARACTERISTICS
When a fault appears in the power system and some areas are disconnected, the
remaining generators connected to the network normally must supply the area which has
been disconnected from utility side supply and there is an instantaneous demand of power
that the generators must tackle. The excitation and the mechanical systems are not so
quick to deliver such huge demand of power even if there is enough reserve. The worst
situation is suffered by the rotors of the generator units. They suffer a torsion torque that
can even break it with the subsequent damage not only for the generator but for the entire
power plant too.
Figure 3.2.15.2-83 Generator islanding occurs.
In example case above, only phase-to-phase voltages L1-L2 and L3-L1 have been
reduced and the voltage L2-L3 remains the same. This means that the problem happened