Application Guide - NP900 Series
450 (504
)
A996A
For very high overvoltage AVR has an instant low function which lowers the voltage
without any given set time delay except the given minimum time between control pulses.
This function is used in the AVR until the measured voltage is below the set instant low
threshold level. After the set instant low threshold level is reached corresponding window
time characteristics calculate the consecutive time delays until the desired target window
is reached.
Figure 3.6.7.1-216 Instant low command utilized in addition to two time delayed
windows.
Pick up setting recommendation for the instant low function is
maximum allowed
overvoltage subtracted with tap effect
. By this way there should not be situation where the
voltage is allowed pass longer time over the maximum allowed voltage. For example if the
maximum allowed overvoltage is 10% by local standards and tap effect for the transformer
is 1.67% instant low function pick-up should be set 10% - 1.67% = 8.33%.
Содержание NP900 Series
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Страница 49: ...Application Guide NP900 Series 49 504 A996A Figure 3 2 1 3 25 Definite time operating characteristics...
Страница 50: ...Application Guide NP900 Series 50 504 A996A Figure 3 2 1 3 26 IEC predefined characteristics NI VI LTI and EI...
Страница 52: ...Application Guide NP900 Series 52 504 A996A Figure 3 2 1 3 28 IEEE predefined characteristics EI MI and VI...
Страница 243: ...Application Guide NP900 Series 243 504 A996A Figure 3 3 2 1 122 NPS biased thermal trip curves with kNPS values 7 and 10...
Страница 491: ...Application Guide NP900 Series 491 504 A996A 3 7 5 6 SETTING EXAMPLE...
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