ABB RELION 620 Series Technical Manual page 905

1MRS757644 F
6.5.3
6.5.4
620 series
Technical Manual
Functionality
The fuse failure supervision function SEQSPVC is used to block the voltage-
measuring functions when failure occurs in the secondary circuits between the voltage
transformer (or combi sensor or voltage sensor) and protection relay to avoid
misoperations of the voltage protection functions.
SEQSPVC has two algorithms, a negative sequence-based algorithm and a delta
current and delta voltage algorithm.
A criterion based on the delta current and the delta voltage measurements can be
activated to detect three-phase fuse failures which usually are more associated with
the voltage transformer switching during station operations.
Operation principle
The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of SEQSPVC can be described with a module diagram. All the modules
in the diagram are explained in the next sections.
GUID-27E5A90A-6DCB-4545-A33A-F37C02F27A28 V1 EN
Figure 470: 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.
Section 6
Supervision functions
899