ABB Relion 670 Series Technical Reference Manual page 505

1MRK505222-UUS C
Normal voltage
IntBlkStVal1
IntBlkStVal2
ANSI05000466 V1 EN
Figure 254: Blocking function
8.1.2.4
Technical reference manual
V Disconnection
Pickup1
Pickup2
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 PICKUP condition. The design of Two step undervoltage protection
UV2PTUV (27) is schematically shown in
tBlkUV1 <
t1,t1Min
tBlkUV2 <
t2,t2Min
Block step 1
Block step 2
Figure
Section 8
Voltage protection
Time
en05000466_ansi.vsd
255.
499