the other values are already available.
On the control back panel, when no source or differential
PT are present, the connection that would be the input for
one of these PTs if they were present is tied to the load-
side PT input. When the load and source PT inputs are tied
and the values are the same, the control interprets that as
meaning that the calculation is required. If the inputs are
not tied when there is no source-side PT signal, the control
will attempt to read the source-side voltage and will provide
an errant value. Often, this value will be in the range of 40
volts. If the source-voltage value is displaying errantly and
there is no source PT, check to make sure the source and
load PT inputs (terminals V7 and VS) are tied together.
Reverse power operation
Most voltage regulators are installed in circuits with well-
defined power flow from source to load. However, some
circuits have interconnections or loops in which the direction
of power flow through the regulator may change. For
optimum utility system performance, a regulator installed on
such a circuit should have the capability of detecting reverse
power flow and of sensing and controlling the voltage,
regardless of the power flow direction.
The control has full reverse power capabilities. For fully
automatic reverse operation, the source voltage must
be available to the control. Refer to
in this section of the
manual.
The control offers nine different response characteristics for
forward and reverse power detection and operation. These
characteristics are user-selectable by programming the
Reverse Sensing Mode (FC 56). The nine modes are Locked
Forward, Locked Reverse, Reverse Idle, Bi-directional,
Neutral Idle, Co-generation, Reactive Bi-directional, Bias
Bi-directional, and Bias Co-generation.
This section will separately explain each mode of operation.
Since the control retains the reverse metered demand
values separate from the forward metered values, the
metering will also be explained for each mode.
In determining power direction the control uses one of two
methods, depending upon the reverse sensing mode in use
and the current level detected. In most cases, the control
senses the real component of the current, then determines
the current direction and magnitude in that direction.
Power direction may also be determined using a test-tapping
routine under certain conditions when the "Bias" reverse
sensing modes are employed.
When the conditions indicate power is flowing in reverse,
the following parameters assume new values and the control
operation is affected accordingly:
Load Voltage
Now sensed from what was previously
the source voltage supply.
Source Voltage Now sensed from what was previously
the load voltage supply.
Load Current
In the forward direction, the current is
used directly as measured. In the reverse
direction, the current is scaled to reflect
the ratio difference between the source
and load side of the regulator, according
to this formula
Q
:
Reverse Load Current =
Load Voltage Supply
Forward
Load
Current
Source
Voltage
Supply
Q
Where source voltage supply and load
voltage supply are in the reverse direction.
Based upon the new metered reverse values, the kVA, kW,
kvar, and % buck/boost are now calculated.
Locked forward mode
The Lock Forward setting is intended for applications where
reverse power flow is not possible. When the control is
set for Locked Forward, a measured voltage from the load
bushing is required, but a source voltage is not required.
METERING: Always determined in the forward direction,
regardless of power flow direction. If reverse power occurs,
the metering functions remain on the normal load side of
the regulator—no reverse demand readings will occur.
125
INSTALLATION, OPERATION, AND MAINTENANCE INSTRUCTIONS
MN225003EN April 2018
CL-7 Voltage Regulator Control