Figure 136: 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.
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
is selected, the reset timer runs until the set
Reset delay time
value is exceeded.
When the IDMT curves are selected, the
Type of reset curve
setting can be set to
"Immediate", "Def time reset" or "Inverse reset". The reset curve type "Immediate"
causes an immediate reset. With the reset curve type "Def time reset", the reset
time depends on the
Reset delay time
setting. With the reset curve type "Inverse
Protection functions
1MRS757644 H
278 620 series
Technical Manual
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