Level detector 1
The calculated compensated unbalance current I_AMPL_COMP is compared to the
set "Start value". If I_AMPL_COMP exceeds the set "Start value", the Level detector 1
sends an enabling signal to the Timer 1 module.
Timer 1
Once activated, the Timer 1 module 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
and
Curve parameter E
.
In a drop-off situation, that is when a fault suddenly disappears before the operate
delay is exceeded, the Timer 1 reset state is activated. The functionality of the Timer
1 in the reset state depends on the combination of the Operating curve type 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, an immediate reset occurs. The START output is deactivated when the
reset timer has elapsed.
The setting
Time multiplier
is used for scaling the IDMT operation and reset times.
The setting parameter
Minimum operate time
defines the minimum desired
operation time for IDMT. The setting is applicable only when the IDMT curves are
used.
The
Minimum operate time
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
Minimum operate time
setting.
The Timer 1 module calculates the start duration value START_DUR, which indicates
the percentile ratio of the start situation and the set operation time. The value is
available in the monitored data view.
In a typical double-Y-connected configuration (
Figure 629
), there are two branches
in every phase and hence six individual counters COUNT_BR1_A, COUNT_BR2_A,
COUNT_BR1_B, COUNT_BR2_B, COUNT_BR1_C and COUNT_BR2_C are maintained.
Based on the phase angle of the compensated unbalance current I_ANGL_COMP,
the phase and the branch of the element failure location is detected. However,
the element failure location also depends on the type of capacitor banks, that is,
whether internal or external fuses are used. The setting
Fuse location
is used to set
the capacitor bank type as “External” or “Internal”.
For an external fuse capacitor bank, the element failure location and corresponding
counters to be incremented are determined based on the phase angle of the
compensated unbalance current.
1MRS759142 F
Protection functions
REX640
Technical Manual
1123
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