failure detection is one of the means to block voltage-based functions before they
operate.
Three phase network
VT
Fault in a measuring
circuit between
voltage transformer
and protection relay
e.g. blown fuse
REF 615
Figure 272: Fault in a circuit from the voltage transformer to the protection relay
A fuse failure occurs due to blown fuses, broken wires or intended substation
operations. The negative sequence component-based function can be used to
detect different types of single-phase or two-phase fuse failures. However, at
least one of the three circuits from the voltage transformers must be intact. The
supporting delta-based function can also detect a fuse failure due to three-phase
interruptions.
In the negative sequence component-based part of the function, a fuse failure is
detected by comparing the calculated value of the negative sequence component
voltage to the negative sequence component current. The sequence entities are
calculated from the measured current and voltage data for all three phases. The
purpose of this function is to block voltage-dependent functions when a fuse
failure is detected. Since the voltage dependence differs between these functions,
SEQSPVC has two outputs for this purpose.
6.2.6 Signals
6.2.6.1 SEQSPVC Input signals
Table 556: SEQSPVC Input signals
Name Type Default Description
I_A SIGNAL 0 Phase A current
I_B SIGNAL 0 Phase B current
I_C SIGNAL 0 Phase C current
I
2
SIGNAL 0 Negative sequence
current
U_A_AB SIGNAL 0 Phase A voltage
U_B_BC SIGNAL 0 Phase B voltage
Table continues on the next page
1MRS758755 C Supervision functions
REC615 & RER615
Technical Manual
539
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