Blocking; Design - ABB REG650 Technical Manual

1MRK 502 034-UEN -
8.1.7.3
8.1.7.4
Technical Manual
The lowest voltage is always used for the inverse time delay integration. The
details of the different inverse time characteristics are shown in section
"Inverse time characteristics".
Trip signal issuing requires that the undervoltage condition continues for at least
the user set time delay. This time delay is set by the parameter t1 and t2 for definite
time mode (DT) and by some special voltage level dependent time curves for the
inverse time mode (IDMT). If the start condition, with respect to the measured
voltage ceases during the delay time, the corresponding start output is reset.

Blocking

It is possible to block Two step undervoltage protection (UV2PTUV) partially or
completely, by binary input signals or by parameter settings, where:
BLOCK:
BLKST1:
BLKST2:

Design

The voltage measuring elements continuously measure the three phase-to-neutral
voltages or the three phase-to-phase voltages. Recursive fourier filters or true RMS
filters of input voltage signals are used. The voltages are individually compared to
the set value, and the lowest voltage is used for the inverse time characteristic
integration. A special logic is included to achieve the 1 out of 3, 2 out of 3 and 3
out of 3 criteria to fulfill the START condition. The design of Two step
undervoltage protection UV2PTUV is schematically shown in
blocks all outputs
blocks all start and trip outputs related to step 1
blocks all start and trip outputs related to step 2
Section 8
Voltage protection
20.3
Figure 115.
221