The start value multiplication is normally done when the inrush detection function
(INRPHAR) is connected to the ENA_MULT input.
Figure 208: Start value behavior with ENA_MULT input activated
Phase selection logic
If the fault criteria are fulfilled in the level detector and the directional calculation,
the phase selection logic detects the phase or phases in which the measured
current exceeds the setting. If the phase information matches the
Num of start
phases
setting, the phase selection logic activates the timer module.
FAULT_DIR gives the detected direction of the fault during fault situations, that is,
when the START output is active.
Timer
Once activated, the timer activates the START output. Depending on the value of the
Operating curve type
setting, the time characteristics are according to DT or IDMT.
When the operation timer has reached the value of
Operate delay time
in the DT
mode or the maximum value defined by the inverse time curve, the OPERATE output
is activated.
When the user-programmable IDMT curve is selected, the operation time
characteristics are defined by the parameters
Curve parameter A
,
Curve parameter
B
,
Curve parameter C
,
Curve parameter D
and Curve parameter E.
If a drop-off situation happens, that is, a fault suddenly disappears before the
operate delay is exceeded, the timer reset state is activated. The functionality of
the timer in the reset state depends on the combination of the
Operating curve
type
,
Type of reset curve
and
Reset delay time
settings. When the DT characteristic
1MRS759142 F
Protection functions
REX640
Technical Manual
349
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