Protection Functions
46 PRS-7367
selection detects the phase or phases in which the measured current exceeds the setting. If the
phase information is equal to or more than the 67P_Str_Ph_Num setting, the initiation logic output
signal is activated.
67P_Str_Ph_Num shows the number of phases required for operate activation.
 Timer element
The functional module diagram is shown as below:
Figure 3.3-6 Functional module diagram
Once initiation logic is fulfilled and no 67P_Blk signal is activated, the 67P_Str signal is set. The
67P_Str_A, 67P_Str_B and 67P_Str_C outputs are used to indicate which phases are started.
The timer mode is determined by IDMT curves for over quantity protection.
The operation is activated after the operation timer has reached the calculated value. However,
67P_Min_Op_T defines the minimum desired operate time for IDMT. If a drop-off situation
happens, that is, a fault suddenly disappears before the operate delay is exceeded, the operation
will reset after the set value 67P_Reset_T is exceeded.
NOTICE!
The 67P_Min_Op_T setting should be used with great care because the operation time
is according to the IDMT curve, but always at least the value of the 67P_Min_Op_T
setting.
67P can be blocked from 67P_Blk. The activation of 67P_Blk input deactivates all outputs and
resets internal timers.
ï‚ž The start signals from the function can be blocked from 67P_Blk_Str, the binary input.
ï‚ž The operation signals from the function can be blocked from 67P_Blk_Op, the binary input.
3.3.3 67P Application Scope
67P is used as short-circuit protection in three-phase distribution or sub transmission networks
operating at 50 or 60 Hz. In radial networks, phase overcurrent IEDs are often sufficient for the
short circuit protection of lines, transformers and other equipment.
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