Line Drop Compensator - Cooper VR-32 Installation, Operation And Maintenance Instructions

VR-32 Regulator and CL-2A Control
Figure 2-6.
Nameplate.
The voltage developed by the sensing winding is brought
from the tap changer terminal board to the junction box termi-
nal board, through the control cable, into the enclosure, and
terminates at the knife switch labeled V 1 . Opening this knife
switch provides a visible means of removing all power to the
control and back panel, thus allowing the operator to work
safely on the control circuitry while the regulator is energized.
From the knife switch, the voltage is ratio corrected by the
RCT as previously described. Note, also, that a separation of
sensing and motor circuits occurs at this transformer. The
motor circuit is routed directly to the control front panel, where-
as the sensing potential is brought back to the top terminal
strip, through a series of removable jumpers, and then to the
front panel. These jumpers permit the easy addition of acces-
sories which compliment the control (voltage limiter, voltage
reduction, metering).
Both of the voltage sources are protected against surges on
the control front panel, through the use of metal oxide varis-
tors. These potentials are then connected directly to the power
switch. Note that the power switch has three positions: INTER-
NAL/OFF/ EXTERNAL. The INTERNAL position powers the
control from the regulator sensing winding, and the EXTER-
NAL position permits an external 120V supply be used to
operate the the regulator and control. When the power switch
is in the EXTERNAL position, the internal supply is discon-
nected to prevent accidentally energizing the high voltage
winding and bushings. The external source terminals are
prominently located adjacent to the voltmeter test terminals.
The voltmeter terminals allow the monitoring of the voltage
that is applied to the sensing input transformer.
The two voltage circuits are routed from the power switch to
the respective 6 amp motor fuse and 2 amp panel fuses. From
the fuse, the motor potential provides power to the auto/manu-
al selector switch, the drag hand reset solenoid, the neutral
light, and the holding switch (alternate motor source) circuits.
The sensing supply provides power to the printed circuit
board. This function is described further in the following sec-
tion.
2-9
Line Drop Compensator (Current Circuit)
All VR-32 regulators are designed with an internal current trans-
former for the line drop compensator and optional metering
devices. Table 2-2 provides the application information for the var-
ious C.T.'s used on the Cooper Power regulators. These C.T.'s
provide 200 mA rated secondary output for the full load C.T. pri-
mary current.
The current developed by the C.T. is brought to the junction
box terminal board, through the control cable into the enclosure,
and terminates at the knife switch labeled C. Closing the knife
switch provides a visible means of shorting the C.T., thus allowing
the operator to work safely on the current circuitry. (For additional
safety measures, the V 1 knife switch should also be opened.) At
this knife switch, one side of the C.T. is connected to the equip-
ment ground, and is also routed to the front panel for connection
to the auxiliary current transformer (ACT). The "high" side of the
current circuit is brought to the top terminal strip, through a series
of removable jumpers, and then to the front panel for connection
to the ACT. These jumpers, permit the easy addition of acces-
sories which compliment the control (Meter Pac).
The auxiliary current transformer provides isolation and current
transformation from the 200 mA base to 50 mA for the line drop
compensation elements. The output from this transformer passes
first to the line drop compensator (LDC) control switch before
flowing to the resistance and reactance components. The LDC
switch provides the ability to bypass the LDC circuit entirely (off
position), and change the current direction through either the
resistance element (R) or the reactance element (X). This is illus-
trated by the switch senings +X+R, -X+R, +X-R.
As current flows through the regulator on the primary circuit, a
proportional current (on the 200 mA base) is developed in the
C.T. secondary. This provides a current flow through the resistive
and reactive elements which produces voltage drops (both R & X)
with polarities as determined by the LDC control switch. This volt-
age subtracts vectorially from the voltage sensing signal output of
the potential transformer. The end result is that the voltage signal
input to the circuit board is altered according to the line current-
flow and the values of the resistance and reactance. settings. In
this manner, the voltage regulator responds to changes in LOAD
as well as changes in VOLTAGE.
TABLE 2-2
Current Tansformer Applications.
R
egulator Current
Ratings
15
50
75
100
150
167, 200
219 231, 250
289 300
328, 334, 347, 400
418, 438, 463, 500
548, 578, 656, 668
833, 875, 1000, 1093
1332, 1665
C.T.
Primary Current
25
50
75
100
150
200
250
300
400
500
600
1000
1600