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the scheme switch [OC1-OPMD]. Conversely, when a trip is only required for faults that occur
in two or more phases, 2OUTOF3 (a fault occurs in two or more phases) is set for the scheme
switch [OC1-OPMD].
Table 2.15-6 Fault type and tripping mode
Note: A tick (✓) indicates that a trip is issued when faults are detected.
A mark (X) indicates the occurrence of a fault on a particular phase. A mark
shown thus (–) indicates that no fault has occurred on that particular phase.
(ii) Blocking OC by ICD
The operation of each OC element can be blocked if the ICD function detects a second
harmonic current caused by the magnetizing inrush current phenomenon when a
transformer is energized. For example, for the OC1 element, the scheme switch [OC1-
2fBlk] is provided, and Block-3P should be set when the user wishes to block all three-
phases of the OC1 element when the second harmonic associated with the magnetizing
inrush current is present. Alternatively, Block-PerP is set if blocking is just required for a
single phase concerting to the phenomenon. Non is set for the scheme switch [OC1-2fBlk]
as the default setting. For more information about the ICD function, see Chapter
Relay
application: Inrush current detection function
.
(iii) Blocking OC by VTF
The operation of the OC element can be blocked by the voltage transformer failure (VTF)
function via a scheme switch. For example, Block can be set for the scheme switch [OC1-
VTFBlk] to block the operation of the OC1 element during a VTF condition. Non is set for
the scheme switch [OC1-VTFBlk] as a default. For more information about the VTF, see
Chapter
Relay application: VT failure detection
.
(iv) OC operation for auto-reclose
The OC element activates the auto-reclose (ARC) function. However, if for example ARC
is not required, Block is set for the scheme switch [OC1-ARCBlk]. Block is set for the
scheme switch [OC1-ARCBlk] as a default.
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