P.8.6
SEL-411L Relay Protection Manual Date Code 20151029
Oscillography, Events, and SER
Duration of Data Captures and Event Reports
total LER period. Table 8.1 shows the relay settings for the data capture
recording times at each effective sampling rate. Traveling wave records have a
fixed sampling rate of 1.5625 MHz and a fixed event length of 7.5 ms.
NOTE: PRE has a dynamic range
based on the current value of LER.
The upper range of PRE = LER – 0.05.
Figure 8.2 Data Capture/Event Report Times
The relay stores all data captures to volatile RAM and then moves these data
to nonvolatile memory storage. There is enough volatile RAM to store one
maximum length capture (maximum LER time) for a given SRATE. No data
captures can be triggered while the volatile RAM is full; the relay must move
at least one data capture to nonvolatile storage to reenable data capture
triggering. Thus, to record sequential events, you must set LER to half or less
than half of the maximum LER setting. The relay stores more sequential data
captures as you set LER smaller.
Table 8.2 lists the maximum number of data captures/event reports the relay
stores in nonvolatile memory for various report lengths and sample rates. The
relay automatically overwrites the oldest events with the newest events when
the nonvolatile storage capacity is exceeded.
The relay stores as many as two back-to-back (approximately six seconds of
data) of high-resolution raw or filtered events (three seconds each) in
nonvolatile memory at the maximum resolution (8000 samples/second
effective sampling rate). Table 8.2 lists the storage capability of the relay for
common event report lengths.
The lower rows of Table 8.2 show the number of event reports the relay stores
at the maximum data capture times for each SRATE sampling rate setting.
Table entries are the maximum number of stored events; these can vary by 10
percent according to relay memory usage.
Table 8.1 Report Settings
Label Description Range Default
SRATE Effective sample rate of event report 1, 2, 4, 8 kHz 2 kHz
SRATE = 8 kHz
LER Length of event report 0.25–3.00 seconds 0.5 seconds
PRE Length of prefault 0.05–2.95 seconds 0.1 seconds
SRATE = 4 kHz
LER Length of event report 0.25–6.00 seconds 0.5 seconds
PRE Length of prefault 0.05–5.95 seconds 0.1 seconds
SRATE = 2 kHz
LER Length of event report 0.25–9.00 seconds 0.5 seconds
PRE Length of prefault 0.05–8.95 seconds 0.1 seconds
SRATE = 1 kHz
LER Length of event report 0.25–12.00 seconds 0.5 seconds
PRE Length of prefault 0.05–11.95 seconds 0.1 seconds
NOTE: Consider the total capture
time when choosing a value for
setting LER at the SRATE := 8 kHz. At
LER := 1.0 or LER := 2.0 the relay
records at least five data captures.
These and smaller LER settings are
sufficient for most power system
disturbances.
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