ABB RELION REX640 Technical Manual page 1333

1MRS759142 F
CB_CLOSED
DISCON_OPEN
MINCB_OPEN
Figure 758: Functional module diagram
Negative phase-sequence criterion
A fuse failure based on the negative-sequence criterion is detected if the measured
negative-sequence voltage exceeds the set
measured negative-sequence current is below the set
The detected fuse failure is reported to the decision logic module.
Voltage check
The phase voltage magnitude is checked when deciding whether the fuse failure is a
three, two or a single-phase fault.
The module makes a phase-specific comparison between each voltage input and
the
corresponding phase is reported to the decision logic module.
Current and voltage delta criterion
The delta function can be activated by setting the
to "True". Once the function is activated, it operates in parallel with the negative
sequence-based algorithm. The current and voltage are continuously measured in all
three phases to calculate:
• Change of voltage dU/dt
• Change of current dI/dt
The calculated delta quantities are compared to the respective set values of the
Current change rate and Voltage change rate settings.
The delta current and delta voltage algorithms detect a fuse failure if there is a
sufficient negative change in the voltage amplitude without a sufficient change in
REX640
Technical Manual
U
U_A_AB
U3P
U_B_BC
U_C_CA
I_A
I_B
I_C
I3P
I
BLOCK
Seal in voltage setting. If the input voltage is lower than the setting, the
Negative
phase
sequence
criterion
2
Voltage
check
Current and
voltage
delta
criterion
2
Neg Seq voltage Lev value and the
Supervision functions
FUSEF_3PH
Decision
logic
FUSEF_U
Neg Seq current Lev value.
Change rate enable parameter
1333