ABB RELION REX640 Technical Manual page 756

Section 4
Protection functions
750
I
2
I
1
I3P
I_A
I_B
I_C
BLOCK
GUID-77CC7147-960F-4055-B5B9-DF9134968B31 V1 EN
Figure 412: Functional module diagram
I /I
2 1
The I /I module calculates the ratio of the negative and positive sequence current. It
2 1
reports the calculated value to the level detector.
Level detector
The level detector compares the calculated ratio of the negative- and positive-
sequence currents to the set Start value. If the calculated value exceeds the set Start
value and the min current check module has exceeded the value of Min phase current,
the level detector reports the exceeding of the value to the timer.
Min current check
The min current check module checks whether the measured phase currents are above
the set Min phase current. At least one of the phase currents needs to be above the set
limit to enable the level detector module.
Timer
Once activated, the timer activates the START output. The time characteristic is
according to DT. When the operation timer has reached the value set by Operate delay
time, the OPERATE output is activated. If the fault disappears before the module
operates, the reset timer is activated. If the reset timer reaches the value set by Reset
delay time, the operate timer resets and the START output is deactivated.
The timer calculates the start duration value START_DUR, which indicates the
percentage ratio of the start situation and the set operation time. The value is available
in the monitored data view.
Blocking logic
There are three operation modes in the blocking function. The operation modes are
controlled by the BLOCK input and the global setting in Configuration/System/
Blocking mode which selects the blocking mode. The BLOCK input can be controlled
by a binary input, a horizontal communication input or an internal signal of the
protection relay's program. The influence of the BLOCK signal activation is
preselected with the global setting Blocking mode.
Level
I /I
2 1
detector
Min
Blocking
current
check
1MRS759142 C
Timer
OPERATE
t
START
logic
Technical Manual
REX640