ABB 615 series Technical Manual page 741

1MAC059074-MB A
615 series ANSI
Technical Manual
V_AB
Under
V_BC voltage
detection
V_CA
V
Reactive
1
power
monitoring
I
1
Blocking
BLOCK
logic
GUID-66E75458-7850-40A5-8BF9-B1577E72D8DB V1 EN
Figure 367: Functional module diagram
Under voltage detection
Under voltage detection compares the fundamental frequency component of all three
phase-to-phase voltages with the set Voltage pickup value. When all three phase-to-phase
voltages are lower than the set Voltage pickup value, the Under voltage detection module
sends an enable signal to the Timer indicating an undervoltage condition at the grid
connection point.
Reactive power monitoring
This module calculates and monitors the reactive power based on positive sequence
current and voltage. The use of a positive sequence component makes the determination
of power insensitive to a possible asymmetry in current and voltages. When the reactive
power exceeds Min reactive power and flows in the operating area, the module sends an
enable signal to the Timer indicating that the reactive power is being consumed at the grid
connection point. A slight tilt in the curve can be obtained by the setting Pwr sector
reduction.
To avoid false tripping, reactive power calculation is blocked if the magnitude of positive
sequence current is less than the set Min PS current.
The magnitude of calculated reactive power Q is available in the Monitored data view.
Timer
TRIP
t
PICKUP
Section 4
Protection functions
735