5.16
SEL-787 Relay Instruction Manual Date Code 20150130
Metering and Monitoring
Through-Fault Event Monitoring
When the fault current falls below 4.5 times the full load level, the element
deasserts, and the following occurs:
➤ The thermal element records the stop time; then calculates (and
records) the fault duration.
➤ The thermal element records the maximum value of the fault
current during the fault.
➤ The integration process stops.
The relay can store (archive) the data of 500 through faults in a first-in-first-
out (FIFO) buffer. The element automatically archives the data when one of
the following conditions is true:
➤ The 10-cycle Timer deasserts and the enable signal is already
de-asserted.
➤ The 10-cycle Timer is already de-asserted and the enable signal
de-asserts.
Through-Fault
Element (TFE) Serial
Command
The format of the TFE command is as follows:
TFE [nnn A|P|C|R]
where:
Figure 5.19 displays the relay response to the TFE (no other parameters)
command. Notice that Winding 1 is the winding whose current inputs the
element uses in the calculations (THFLTD = 1). The TFE command lists as
many as 20 of the most recent through-faults. "Total Number of Transformer
Through Faults:" is the sum of the detected through faults of all three phases
since the last reset, with a maximum of 65,535 counts. "Number of n Phase
Through Faults:" (n = A, B, C) refers to the through faults detected for that
particular phase since the last reset, also with a maximum of 65,535 counts.
The "Total Accumulated Percentage of Through Fault Capability" shows the
per phase value. The value represents the percent amount of through fault
capability used up based on the per unitized capability from the curve of
Figure 5.17. The through-fault alarm state is either a 1 (indicating an alarm
state), or a 0 (indicating a normal state).
nnn Specifies number of through faults to display.
A The relay displays all the Through Fault Records in the
memory.
P Use to specify pre-loading
C or R Sets the accumulated values to 0 and deletes the history.
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