4 Setting Up the MJ-4A & MJ-4B Control Panel
Siemens Energy, Inc. 29
4.4.1 Regulator Setpoints
Regulator setpoints define the operating limits for Auto-
matic mode operation. Two sets of limits are maintained:
one for forward power flow conditions and another for
reverse power flow conditions.
Voltage Level Setpoint
The Voltage Level setpoint defines the nominal level you
wish the regulator to maintain.
Bandwidth Setpoint
The Bandwidth setpoint defines the voltage range within
which the regulator output is maintained. It is divided
equally above and below the Voltage Level setpoint.
For example, a Bandwidth of 6 volts with a Voltage Level
setpoint of 120.0 volts specifies that any load voltage
between 117 volts and 123 volts is “in band.”
Time Delay Setpoint
The Time Delay setpoint defines the amount of time the
controller will wait before commanding a tap change.
4.4.2 Line Drop Compensation
The Line Drop Compensation (LDC) data item defines the
assumed voltage drop between the regulator and the load
center. Settings are expressed in volts.
To specify LDC values, view Fwd Comp (R) for the For-
ward Resistive component and Fwd Comp (X) for the For-
ward Reactive component. In systems with reverse
power flow, view Rev Comp (R) and Rev Comp (X) to
specify the Reverse components.
A Line Drop Calculator software application is available on
the Siemens website. This application automatically calcu-
lates the LDC values when the system parameters are
entered.
Figure 4.5 Flow Chart of VRC Modes
4.4.3 Voltage Reduction Control Items
Voltage Reduction Control (VRC) is used to reduce output
voltage. When activated, VRC has the effect of lowering
the Voltage Level setpoint. Voltage reduction is accom-
plished in one or more discrete steps which are defined as
a percentage of the voltage level setpoint (Fwd Volts, Rev
Volts). VRC operates immediately to reduce output volt-
age without waiting for completion of the Time Delay.
The following sections describe each of the VRC menu
items, and explain how to set them.
ALT Delay
When the VRC2 In item is set for ALT DELAY, an alternate
time delay is used before commanding a tap change when
the VRC2 contacts are closed. When the VRC2 contacts
are open, the standard (Fwd Delay) time delay is used.
VRC Status
The VRC Status data item displays present VRC informa-
tion in the display panel. It can be directly accessed with
the VRC fast-path key, or viewed from the <REGULA-
TOR> Menu.
Information displayed includes: percent reduction pres-
ently in effect (nn.n%), the VRC mode (L - Local, A - Auto-
matic, R - Remote), and the present step/stage (0-3). For
example, if VRC is presently at 5%, Remote, and MJ-X
mode Stage 3, the display panel would show VRC Stat
=05.0%R3.
VRC1 In
This item defines which feature is implemented when the
external terminal block contacts (VRC1) are closed. Select
VRC to enable remote Voltage Reduction Control. Choose
X-COMP to enable reactive compensation polarity control.
When VRC1 contacts are closed, the LDC polarity is
reversed.
VRC2 In
This item defines which feature is implemented when the
VRC2 contacts are closed. Choose VRC to enable remote
Voltage Reduction Control. Choose ALTDELAY to use the
ALT Delay feature described above. Choose LO XBATT to
use these terminals for monitoring status change (close to
open or vice versa). Choose AUTO INH to inhibit the pro-
cessor from making automatic tap changes.
VRC Mode:OFF VRC Mode:Local
Local VRC%:XX.X VRC Remote:MJ3A
MJ-3A VRC%XX.X
VRC Mode:Remote
VRC Remote:MJ-X
VRC Stage1:XX.X
VRC Stage2:XX.X
VRC Stage3:XX.X
VRC Mode:Aut/Rem
AutoVRCset1:XX.X
AutoVRCset2:XX.X
AutoVRC1 %I:XX.X
AutoVRC2 %I:XX.X
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