Hitachi Relion 650 Series Technical Manual page 298

Section 12
Monitoring
IEC19000769 V1 EN-US
Figure 134: Detection of precise load voltage interruption instant for capacitive load
The function initially detects the breaker state change from the RMS value of the load voltage
feedback signal: The breaker is assumed open as soon as the RMS value drops below the absolute
OpenCThreshold value. (A capacitive load will usually retain a trapped DC charge after current
interruption. Still, the measured voltage will decay to zero quickly because the primary VT and the
input VT on the TRM cannot transmit DC voltage.) From the instant of open state detection, the
function backtracks the voltage samples from the last 5 power cycles.
Specifically, it evaluates the difference between absolute values of each sample and the sample
exactly nominal half power cycle back (Δx as shown in
differences is greater than or equal to OpenFThreshold, the earliest of the five samples with its
corresponding timestamp is considered the interruption instant.
In addition to the actual values, ACBMSCBR also provides the predicted interruption time and
predicted arcing time for the operation, as detailed in
given on receiving the trip command OPCMDINP, and the actual values are given as soon as the
interruption is detected.
ACBMSCBR also evaluates the instantaneous, peak and RMS of the interrupted current at the
instant of current interruption and publishes them at its outputs LOOPILX, LOOPPILX and SWALX
respectively, until the next switching operation.
At the detected instant of current interruption, ACBMSCBR stores the instantaneous value and
publishes it at LOOPILX. Similarly, ACBMSCBR scans through the current samples from the
controlled trip command COPCMDLX till the detected instant of current interruption to determine the
instantaneous peak value of the interrupted current (LOOPPILX). Based on the monitored peak value
as described above, the RMS value of interrupted current (SWALX) is evaluated assuming a
sinusoidal waveform.
Re-strike/Re-ignition detection
A circuit breaker is said to re-ignite or re-strike if, during an opening operation, current is initially
interrupted but starts flowing again shortly thereafter, as shown in
292
z
z
5
z
4
z
z 3
2
1
Half Power Cycle time
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Δx = ||y |– |z ||
1 1 1
Δx = ||y |– |z ||
2 2 2
Δx = ||y |– |z ||
3 3 3
Δx = ||y |– |z ||
4 4 4
Δx = ||y |– |z ||
5 5 5
Figure 134). If the average of five consecutive
Section 12.18.7.11.2. The predicted values are
1MRK 511 557-UEN Rev. A
y y y y y
1 2 3 4 5
IEC19000769-1-en.vsdx
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Figure 135.
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