Table 970: Analog Inputs
Input Description
I3P Three phase currents
U3P Three phase voltages
Table 971: Special conditions
Condition Description
U3P connected real measurements The function requires that at least two volt-
age channels are connected
Improper analog channel configuration causes a validation error if the analog
channels are not completely configured or they do not match with certain settings.
4.7.5.5 Operation principle
The
Operation
setting is used to enable or disable the function. When selected "On"
the function is enabled and respectively "Off" means function is disabled.
The operation of DNZPDIS can be described by using a module diagram ( see
Figure
578
below). All the modules in the diagram are explained in the next sections.
BLOCK
OPERATE
Blocking
logic
START
Impedance
calculation
Low Level
blocking
Fault
direction
detector
FAULT_DIR
DIRECTION
U3P
I3P
U
2
I
2
I
1
t
Timer
Figure 578: Functional module diagram
Low level blocking
This module receives positive sequence current (I
1
) and negative sequence current
(I
2
). Both are calculated from fundamental frequency three phase currents.
Low level blocking is used to block the Impedance calculation if negative sequence
current does not satisfy minimum level criteria. If negative sequence current
exceeds setting
Min Ng Seq current Fw
value, impedance calculation is allowed in
forward direction. Alternatively, if negative sequence current is exceeds setting
Min
Ng Seq current Rv
value, impedance calculation is allowed in reverse direction.
The negative sequence current to positive sequence current ratio (I
2
/I
1
) should also
exceed the setting
Restrain factor
to enable impedance calculation.
1MRS759142 F
Protection functions
REX640
Technical Manual
1039
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