ABB REL650 series Technical Manual page 163

1MRK 506 335-UUS A
Technical manual
Three-phase fault detection
Unless it has been categorized as a single or two-phase fault, the function classifies it as
a three-phase fault if the following conditions are fulfilled:
|V |V1Level
1
and
|I |>I1LowLevel
1
or
|I |>IMaxLoad
1
where:
V | and |I | are the positive sequence voltage and current magnitude
1 1
V1Level ,
are the setting of limits for positive sequence voltage and current
I1LowLevel
IMaxLoad
is the setting of the maximum load current
Fault evaluation and selection logic
The phase selection logic has an evaluation procedure that can be simplified according to
figure 71. Only phase A is shown in the figure. If the internal signal 3 Phase fault is
activated, all four outputs PICKUP, PU_A, PU_B and PU_C gets activated.
Section 6
Impedance protection
157