ABB REO 517, Applications Manual

Page: 151 / 440

141
Inverse time delayed undervoltage
protection (TUV2)
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The inverse time delayed undervoltage protection function, TUV2, is intended for sin-
gle- and two-phase systems and is applicable in all situations, where reliable detection
of low phase voltages is necessary.
Undervoltage protection prevents elements from running under conditions that could
cause their overheating and thus shorten their life expectancy below the economical
limits.
Undervoltage protection with inverse time delay makes it possible to better adapt the
operate time of the protection to the equipment withstand for different undervoltage
values, than what can be achieved with independent time delay.
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The voltage measuring elements within one of the built-in digital signal processors con-
tinuously measure the phase-to-neutral voltage. The voltage signal is extracted using a
Fourier recursive filter.
If the voltages UL1 or UL2 falls below the set characteristic value U<Inv, respective
timers start the operating time calculation. The operate time depends on the magnitude
of the voltage and the time multiplicator k-value. When the condition for operation is
met, the output signal TUV2-TRIP is activated for 500 ms.
An external signal connected to the input TUV2-BLOCK or TUV2- VTSU blocks the
operation. The signal TUV2-VTSU is normally connected to the fuse failure supervi-
sion function.