Design - ABB Relion Technical Manual

Section 9
Voltage protection
9.1.7.4
286

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 Figure
VA or VAB
Comparator
V < Pickup1
VB or VBC
Comparator
V < Pickup1
VC or VCA
Comparator
V < Pickup1
MinVoltSelector
Comparator
V < Pickup2
Comparator
V < Pickup2
Comparator
V < Pickup2
ANSI08000016 V3 EN
Figure 132: Schematic design of Two step undervoltage protection UV2PTUV (27)
132.
Phase A
Voltage Phase
Selector
OpMode1
Phase B
1 out of 3
2 out of 3
Pickup
Phase C
3 out of 3
&
Trip
Output
Logic
PICKUP
Step 1
Time integrator
TRIP
or Timer t1
Phase A
Voltage Phase
Selector
OpMode2
Phase B
1 out of 3
2 out of 3
Pickup
Phase C
3 out of 3
&
Trip
Output
Logic
PICKUP
Step 2
Timer
TRIP
t2
1MRK 502 048-UUS A
PU_ST1_A
PU_ST1_B
PU_ST1_C
OR
OR
OR
OR
PICKUP
OR
TRIP
OR
ANSI08000016-3-en.vsd
Technical manual