Section 4 1MAC309294-MB F
Protection functions
254 RER620
Technical Manual
Figure 124: Functional module diagram
Buffering logic
This module buffers the three phase voltage and current phasor input values (DFT values
of V_A, V_B, V_C, I_A, I_B, I_C). Once the phase current magnitude is more than the
Phase Level setting the pre-fault buffer will freeze and updating of fault buffer will be
started. The fault buffer will freeze once the buffer is updated fully. The fault location
algorithm will be started only if Relay Trip signal is detected.
Fault loop determination
Any fault can be categorized as either a phase to phase fault or a phase to ground fault.
The fault loop determination algorithm determines whether the fault is a phase to ground
fault or phase to phase fault by comparing the phase currents with zero sequence current.
This module determines the fault loop from pre-fault and fault phasor stored in the
respective buffers. The fault typing is the procedure to identify the type of fault and
therefore the respective voltage and current phasor can be selected from the pre-fault and
fault buffers, for the fault location algorithm.
Once the fault has been classified as either a phase to ground or phase to phase fault, then
the specific fault loop is determined by comparing all phase currents with the setting Phase
Level. Fault loop determination is done in accordance with Table 267.
V_A
V_B
I_A
I_B
I_C
FLT_DIST
FLT_LOOP
FLT_R
XF_LOOP
Buffering
logic
Fault
loop
determination
Fault
location
V_C
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