2 Using the MJ-4A & MJ-4B Operator Panel and Controls
Siemens Energy, Inc. 9
When the real component of load current drops below 1%
of rated current, the RPF indicator continues to display its
previous state.
If the real component of current is less than 1% when the
MJ-4
Control Panel is powered up, the RPF LED is OFF
(indicates forward).
Remote Auto Inhibit LED
This indicator is illuminated when automatic tap changes
are inhibited. Either the remote operator has sent an auto-
matic inhibit command, the Automatic Inhibit contacts
have been activated, or a local operator has pressed the
Auto/Manual pushbutton.
Remote Disabled LED
This indicator is illuminated when Remote control is dis-
abled. When Remote control is enabled a remote operator
can change the settings, configuration, and control the
regulator remotely. When Remote control is disabled, a
remote operator can only view the status of the control
panel. Only a local operator can change the Remote con-
trol status by using the Remote/Local Switch pushbutton.
Band Indicator LEDs
Three Band Indicators, “High", "In Band,” and “Low,” are
located at the top of the front panel. The microprocessor
continuously compares load voltage (corrected for line
drop) against the Voltage Level and Bandwidth setpoints.
The Band Indicator LEDs show the results of this compari-
son (see Table 2.2).
“In Band” indicates that regulator output voltage is within
voltage and bandwidth setpoints.
“High” indicates that regulator output voltage is out-of-
limits on the high side.
“Low” indicates that regulator output voltage is out-of-lim-
its on the low side.
In all power flow modes except Neutral Reverse, if one of
the three Band Indicators is flashing, it is an indication that
tap changes are being inhibited by the control program. In
Neutral Reverse, the flashing Band Indicator in conjunction
with a Reverse Power Flow condition may mean that the
control program is returning the tap position to Neutral.
In the above table, the indicator that is flashing or is on
solid is the respective Band Indicator (High, Low, or In
Band). If all band indicators are off, it is an indication that
Voltage Limit Control (VLC) is active, and compensated
regulator output voltage is higher than the VLC upper limit,
or lower than the VLC Lower limit.
Figure 2.3 Band Indicators and VLC Indicators
Raise / Lower LED Indicator
The Raise / Lower indicator remains on continuously
whenever the tap changer motor is raising or lowering the
tap position. The Raise / Lower indicator can be config-
ured to Flash whenever the tap changer motor is lowering
the tap position. By choosing the setting under the<ADV
CONFIGURE> menu LowerLED.
Table 2.2 Band Indicator Status
Power Flow
Mode
Band Indicator Status
RPF active
and current
magnitude
exceeds I
Threshold %
RPF or FPF
with current
magnitude
below I
Threshold %,
but not = 0
FPF active
and current
magnitude
exceeds I
Threshold %
Neutral R Flash Flash On solid
Idle R Flash Flash On solid
Co-Gen On solid Flash On solid
Bi-Dir On solid Flash On solid
F Lock Flash On solid On solid
R Lock On solid On solid Flash
Table 2.2 Band Indicator Status
Power Flow
Mode
Band Indicator Status
RPF active
and current
magnitude
exceeds I
Threshold %
RPF or FPF
with current
magnitude
below I
Threshold %,
but not = 0
FPF active
and current
magnitude
exceeds I
Threshold %
MJ-4A & MJ-4B Band Indicators
VLC Upper
VLC Lower
Bandwidth
"In-Band"
Indicator
"High" Band
Indicator
VLC Upper
Indicator
"Low" Band
Indicator
VLC Lower
Indicator
Voltage Level
Setpoint
1v
1v
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