upper and lower band edges. When the output voltage is
within this "grey zone", the control will not perform any tap
changes the would take the output voltage over the limit. If
the voltage is directly on the inner edge of the grey zone,
the control will allow one tap change to permit the voltage
to enter the grey zone by as much as 0.7 V.
Voltage reduction
An ideal application for system load management is
at the distribution voltage regulator. Voltage reduction
capabilities within the regulator control permit it to trigger
the regulator to reduce voltage during situations where
power demands surpass the available capacity and where
there are extraordinary peak loads. The control offers three
modes of voltage reduction: Local/Digital Remote, analog
Remote/Latch, and analog Remote/Pulse. All modes operate
for forward or reverse power flow conditions. For further
information on the Local/Digital Remote mode, see below.
Remote/Latch and Remote/Pulse are discussed in the
Analog SCADA section starting later in this section.
All voltage reduction modes work by calculating an effective
set voltage as follows:
Effective Set Voltage = Set Voltage x [1- (% reduction)]
Example: If the set voltage = 123 V and voltage reduction of
4.6% is active, the regulator will regulate the compensated
voltage to 117.3 V, that is, tap down 5.7 V.
While any mode of voltage reduction is in effect, the
Voltage Reduction indicator LED on the front panel will
be illuminated. Voltage reduction occurs after a time out,
as established by the time delay, FC 3 or FC 53, and the
Control Operating Mode, FC 42. The percent reduction in
effect is displayed at FC 71.
Local/digital remote mode
Voltage reduction can be performed by selecting the Local/
Digital Remote mode of operation at FC 70 and then
entering into FC 72 the amount of reduction required as a
percentage of the set voltage. To turn voltage reduction off,
set FC 70 to “Off” or set FC 72 to 0%. The settings may be
changed at the front panel (Local) or through digital SCADA
(Digital) to achieve the desired voltage reduction.
Soft ADD-AMP feature
This feature (FC 79) allows the user to set the regulator for
the Soft ADD-AMP feature locally at the control as well as
remotely through SCADA. The Soft ADD-AMP limits can
be overridden by a local operator running the tap-changer
in manual mode of operation. This is not the case for the
“hard” ADD-AMP limit switches on the position indicator
face. The Soft ADD-AMP feature can be overridden via
digital SCADA if the ADD-AMP mode is set to Remote
Override.
In addition to using to the standard Soft ADD-AMP setting
using FC 79, Configurable Logic Activate ADD-AMP is
available as an advance control feature. It allows the control
to sense system and voltage regulator conditions and
turn on the Soft ADD-AMP feature in reaction to specified
conditions. Configurable Logic Activate ADD-AMP is
controlled by the configurable logic capabilities of the CL-7
control. Configurable logic is described in more detail in
document MN225015EN, CL-7 Regulator Control ProView
NXG Software Programming Guide.
Adaptive ADD-AMP
Adaptive ADD-AMP is a form of the Soft ADD-AMP feature
that enables the control to automatically adapt to the load
being experienced by the regulator and limit the range
of regulation in response. When limiting the range of
regulation, the control adapts the voltage regulator current
rating to meet changing current demands. The control
supports four configurable Adaptive ADD-AMP tap position
levels. To enable the feature the following control settings
are required:
1. Enter the 55 °C AWR current rating of the regulator at
FC 45.
2. Enter the Adaptive ADD-AMP values at FC 45. The
levels can be found in the lower right corner of the unit
nameplate in the chart labeled "Limit Switch Settings
on Position Indicator." The levels correspond to the
nameplate information as follows:
5 % corresponds to position limits of ±8.
6-1/4 % corresponds to position limits of ±10.
7-1/2 % corresponds to position limits of ±12.
8-3/4 % corresponds to position limits of ±14.
3. Set FC 79 SOFT-ADD-AMP Limits to Adaptive.
Supervisory control and data acquisition (SCADA)
With its tap-changer, potential transformer, and current
transformer, the regulator is a likely candidate for a
Supervisory Control and Data Acquisition system where
the utility needs to have centralized voltage control for peak
shaving, energy conservation, or other purposes.
Regulators can be connected to Analog SCADA systems
where the regulator is controlled by contact closure and
the feedback is via a voltage transducer connected to the
voltage sensing circuit of the regulator control. The CL-7
control has a number of features which allow it to function
well on these types of systems. For details, see Analog
SCADA in this section.
The CL-7 control is also capable of real-time digital two-way
communication. For details, see Digital SCADA in this
section.
The control is also well suited to the user who does not
have a SCADA system but does have a need for detailed
information about the bus or feeder loading. For details, see
Data retrieval and settings uploading.
Data retrieval and settings uploading
The CL-7 control is equipped with a USB (type B) PC data
port. It allows for temporary connection to a PC. Using
ProView NXG software, the connection allows the user to
reset all metering and tap position maximum and minimum
139
INSTALLATION, OPERATION, AND MAINTENANCE INSTRUCTIONS MN225003EN April 2018
CL-7 Voltage Regulator Control
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