Sel SEL-787 - Page 355

9.7
Date Code 20150130 Instruction Manual SEL-787 Relay
Analyzing Events
Event Reporting
Analog Event Reports (EVE Command)
The Analog Event Report includes:
➤ Analog values of Winding 1 and 2 currents; IAW, IBW, ICW,
IGW, (IGW only if voltage card is not used), neutral current IN
(if available), voltages and frequency (if voltage card is used)
➤ Digital states of the base model digital inputs (2) and digital
outputs (3)
➤ Event Summary
➤ Relay Settings
If the winding phase CTs are delta connected, the primary currents displayed
are derived from the secondary values by multiplying them with CTR (CT
ratio) and dividing them by the square root of 3. The phase angles shown are
the same as the secondary values. If the CT connection type is known (DAB or
DAC), the user can correct the phase angles. The MET response is meant to
show steady-state primary values. During unbalanced conditions the primary
line currents cannot be reproduced accurately because the delta-connected
CTs filter out the zero-sequence component of the line current. Wye-
connected CTs do not have any such issue.
Filtered and Unfiltered Analog Event Reports
The SEL-787 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
Raw event reports display one extra cycle of data at the beginning of the
report.
Also, unlike the filtered report, the raw event report shows the actual relay
terminal voltage inputs so if the external connections are for DELTA input,
VA = Vab, VB = 0, VC = –Vbc (in primary volts).
Analog Event Report Column Definitions
Refer to the example analog 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 analog values, including ac current, ac voltage, and
frequency, followed by base model input and output information.
NOTE: Figure 9.3 is on multiple
pages.