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Each measurement is taken by inserting one dc
probe (voltmeter) into Common, and the other dc
probe at the voltage being measured.
4.5
FRONT PANEL OPERATION
The front (operator) panel provides a convenient
means of checking or changing settings, and for
checking relay unit operations after a fault. Informa-
tion on fault location, trip types, phase, operating
units, and breakers which tripped become available
by using the pushbuttons to step through the infor-
mation. Targets (fault data) from the last two faults
are retained, even if the relay is deenergized. The
operator is notified that targets are available by a red
flashing LED on the front panel; in addition, alarm 2
output-relay contacts are provided for the external
annunciators.
The operator can identify nonfault voltage, current
and phase angle on the front panel display. Settings
can be checked easily, however, any change to the
settings requires the use of the pushbuttons. When
relay is in the normal operating mode, it is good prac-
tice to set the LED on the Volts/Amps/Angle mode.
4.5.1 Settings Mode
In order to determine the MDAR settings that have
been entered into the system, continually depress
the "DISPLAY SELECT" pushbutton until the "SET-
TINGS" LED is illuminated. Then depress the
"FUNCTION RAISE" or "FUNCTION LOWER" push-
button, in order to scroll through the MDAR SET-
TINGS functions (see Table 4-1). For each settings
function displayed, depress the "VALUE RAISE" or
"VALUE LOWER" pushbutton in order to scroll
through the MDAR values available for the particular
function. (Each value that appears, as each different
function appears in the function field, is considered
to be the "current value" used for that particular func-
tion.)
In order to change the "current value" of a particular
settings function, "RAISE" or "LOWER" the FUNC-
TION field until the desired function appears (e.g.,
"RP"). Then "RAISE" or "LOWER" the values in the
VALUE field until the desired value appears. If the
"ENTER" pushbutton (recessed for security purpos-
es) is depressed, the value which appears in the
VALUE field will replace the "current value" in mem-
ory; but only if the "VALUE ACCEPTED" LED flash-
(5/92)
es once to indicate that the value has been success-
fully entered into the system.
For reasons of security, a plastic screw is used to
cover the ENTER pushbutton. A wire can be used to
lock the plastic screw and to prevent any unautho-
rized personnel from changing the settings.
4.5.2 Metering (Volts/Amps/Angle) Mode
When the Volts/Amps/Angle LED is selected by the
"Display Select" pushbutton, the phase A, B, C volt-
ages, currents and phase angles are available for
on-line display during normal operation. All mea-
sured values can be shown by scrolling the "Raise"
or "Lower" pushbutton in the FUNCTION field. The
values on the display are dependent on the settings
of RP (read primary); RP= YES for the primary side
values and RP = NO for the secondary values. Con-
ditions such as loss-of-potential, loss-of-current and
out-of-step blocking can also be monitored. The
function names and values are shown in Table 4-2.
NOTE: All displayed Phase Angles use V
reference.
4.5.3 Target (Last and Previous Fault) Mode
The MDAR system saves the latest 16 faults
records. The "LAST FAULT" information is of the
most recent fault, the "PREVIOUS FAULT" informa-
tion is of the fault prior to the "LAST FAULT". These
displays contain the target information along with the
"frozen" data at the time of trip. The "LAST FAULT"
register shows one or two records stored by flashing
the LED once or twice per second, respectively.
These records can be deleted by External Reset
voltage TB/5 (+) and TB5/6 (-) or through a remote
communication interface. The front panel (RESET)
pushbutton allows the user to reset the flashing LED
to Metering position only. It will not erase the fault in
formation.
Different types of faults with related descriptions are
shown in Table 4-3. As soon as a fault event is de-
tected, the most recent two sets of target data are
available for display. If the FDAT is set at "TRIP", the
"Last Fault" is the data associated with the most re-
cent trip event. The "Previous Fault" contains the
data from the prior trip event. If a single fault occurs,
the "Last Fault" LED flashes. If a reclosing is applied
and the system trips, the original "LAST FAULT" in-
formation will be transferred to the "Previous Fault"
I.L. 40-385.1B
as
A
4-3
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