Level
detector
IRES
BLOCK
ENA_MULT
t
Timer
t
OPERATE
START
Io
Blocking
logic
Figure 253: Functional module diagram
Level detector
The measured residual current is compared to the set
Start value
. If the measured
value exceeds the set
Start value
, the level detector sends an enable-signal to the
timer module. If the ENA_MULT input is active, the
Start value
setting is multiplied by
the
Start value Mult
setting.
The protection relay does not accept the
Start value
or
Start value Mult
setting if the product of these settings exceeds the
Start value
setting
range.
The start value multiplication is normally done when the inrush detection function
(INRPHAR) is connected to the ENA_MULT input.
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
reset", the reset time depends on the current during the drop-off situation and the
value of START_DUR. The START output is deactivated when the reset timer has
elapsed.
Protection functions
1MRS759142 F
442 REX640
Technical Manual
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