Current
reversal
logic
Weak end
infeed
logic
OPR_IRV
BLK_IRV
IRV
BLK_WEI1
CR
CB_OPEN
U_AB
U_B
U_C
U3P
ECHO
OPR_WEI
CR
BLK_WEI2
FF
BLOCK
U_A
U_BC
U_CA
Figure 717: Functional module diagram
Current reversal logic
Current reversal logic is enabled by changing the value of the
Reversal mode setting
to "On".
This logic uses the start signal of the reverse-looking zone (Z3) connected to the
IRV
input, which is used to recognize the fault in the reverse direction, that is, in the
parallel feeder. When the reverse zone is activated after a start delay (the
Reversal
time setting), the logic is ready to issue an
OPR_IRV
output signal. The
OPR_IRV
signal is connected to the
BLK_CS_OPR
input of DSOCPSCH in order to block the
sending of the carrier send signal (CS) and the activation of the
OPERATE
output of
the communication logic. The
OPR_IRV
signal has a drop-off delay defined with the
Reversal reset time setting.
An internal 10 ms drop-off timer enables the current reversal logic to be
activated for the short-duration input signals even if the
Reversal reset
time setting is set to zero.
The
BLK_IRV
input is used to block the activation of the
OPR_IRV
output. The
BLK_IRV
input is typically connected to the forward-looking zone start signals
within the terminal. General blocking is achieved by activating the
BLOCK
input.
Weak-end infeed logic
Weak-end infeed logic is used to activate the distance protection function when
the fault current infeed is too low due to, for example, high source impedance or
fault current distribution between sources. When activated, the CR signal is logically
combined with the local criteria to initiate the tripping of the weak-end breaker. The
received signal is echoed back to accelerate the tripping in the opposite end with
the stronger source.
1MRS759142 F
Protection related functions
REX640
Technical Manual
1267