ABB RELION 620 Series Technical Manual page 610

Section 6
Supervision functions
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Figure 308: 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 Neg Seq voltage Lev value and the measured
negative-sequence current is below the set Neg Seq current Lev value. 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 Seal
in voltage setting. If the input voltage is lower than the setting, the corresponding phase
is reported to the decision logic module.
Current and voltage delta criterion
The delta function can be activated by setting the Change rate enable parameter 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:
1MAC504801-IB E
620 series ANSI
Technical Manual