Schweitzer Engineering Laboratories SEL-421-4, Instruction Manual

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9.8
SEL-400 Series Relays Instruction Manual Date Code 20171006
Reporting
Duration of Data Captures and Event Reports
To use the data capture functions, select the effective sampling rate and data cap-
ture times. Relay setting SRATE, listed in
Table 9.1 , determines the number of
data points the relay records per second. You can set SRATE to 8 kHz, 4 kHz,
2 kHz, and 1 kHz. The effective sampling rate (SRATE) and the event report
length (LER) are related as follows:
➤
8 kHz sampling—3.00 seconds total event report
➤
4 kHz sampling—6.00 seconds total event report
➤
2 kHz sampling—9.00 seconds total event report
➤
1 kHz sampling—12.00 seconds total event report
The length of the data capture/event report (setting LER) and the pretrigger or
prefault time (setting PRE) are related, as shown in
Figure 9.3 . The LER setting
is the overall length of the event report data capture; the PRE setting determines
the time reserved in the LER period when the relay records pretrigger (prefault)
data. Typically, you set the PRE time to 20 percent of the total LER period.
Table 9.1 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.
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 maxi-
mum 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 of the maximum LER
setting. The relay stores more sequential data captures as you set LER smaller.
Table 9.1 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
Figure 9.3 Data Capture/Event Report Times
PRE
LER
Event Trigger