9.7
Date Code 20080918 Instruction Manual SEL-749M Relay
Analyzing Events
Event Reporting
Filtered and Unfiltered Event Reports
The SEL-749M samples the power system measurands (ac voltage and ac
current) 16 times per power system cycle. A digital filter extracts the
fundamental frequency component of the measurands. The relay operates on
the filtered values and reports these values in the standard, filtered event
report.
To view the raw inputs to the relay, select the unfiltered event report using the
EVE R command. Use the unfiltered event reports to observe power system
conditions:
➤ Power system transients on current and voltage channels
➤ Decaying dc offset during fault conditions on current channels
➤ Power system harmonics (with appropriate analytical PC
software tools)
Raw event reports display one extra cycle of data at the beginning of the
report.
Event Report Column Definitions
NOTE: Figure 9.3 on page 9.11 is on
multiple pages.
Refer to the example event report in Figure 9.3 to view event report columns.
This example event report displays rows of information each 1/4 cycle.
Retrieve this report with the EVE command.
The columns contain ac current, ac voltage, input, output, and protection and
control element information.
Use the serial port SUM command (see SUMMARY Command on
page U.7.26) to retrieve event summary reports.
Current and Voltage Columns. Table 9.2 summarizes the event
summary report current and voltage columns.
Table 9.2 Event Report Current and Voltage Columns
Column
Heading
Description
IA Current measured by channel IA (primary A)
IB Current measured by channel IB (primary A)
IC Current measured by channel IC (primary A)
IG Residual current (IA + IB + IC, primary A)
IN Current measured by channel IN (primary A)
VAN or VAB Voltage measured by channel VAN or VAB (primary V)
VBN or VBC Voltage measured by channel VBN or VBC (primary V)
VCN or VCA Voltage measured by channel VCN or VCA calculated from VAB and
VBC (primary V)
Courtesy of NationalSwitchgear.com
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