3
S225-10-30
!
SAFETY
FOR LIFE
VR-32 Voltage Regulator Potential
Transformer Ratio Test
Purpose
The purpose of this test is to verify proper potential trans-
former ratio.
Required Equipment
• Voltmeter, such as a Fluke 8000 series multimeter
• 120 V variable power supply
• Appropriate cable leads
• Calculator
Procedure
.
Remove the unit from service, as outlined in the
INSTALLATION: Removal from Service
section of
this manual.
2 .
With the regulator in the neutral position, connect 120
V ac between the source "S" and the source-load "SL"
bushings.
3 .
Open the backpanel knife switch marked
V
1
. Measure
the voltage between the top of the
V
1
knife switch and
the top terminal strip ground
TB
1
-G
.
4 .
Note the correct PT ratio as given on the nameplate
under the Internal PT Column.
5 .
Verify the internal tap setting of the PT by inspecting the
top of the tap-changer board located under the regula-
tor cover hand hole. It will be
E
1
,
E
2
,
E
3
, etc. Use the
correct ratio.
6 .
Using the formula in the example below, determine
what the correct output voltage should be and com-
pare it to the actual reading as seen on the voltmeter
across the control test terminals.
Example:
If ratio is shown as 60:1, then the
V
1
to ground voltage will be:
Input Voltage (120 V ac) =
V
1
to ground voltage
PT Ratio
(120 V ac)/(60) =
2.0 V
Contact your Cooper Power Systems representative with
any questions.
Regulator dry-Out Procedure
.
Remove the unit from service, as outlined in the
INSTALLATION: Removal from Service
section of
this manual.
2 .
Conduct this test with the regulator located in a pro-
tected area in the maintenance shop or other suitable
location.
3 .
Place regulator on the
6 Raise
position using the
external source terminals and voltage source.
4 .
Place a jumper, rated for nominal current, between
the source (S) and the load (L) bushings. A clamp-on
ammeter should be used to measure the current in the
shorted current path.
5 .
Ground the regulator tank.
6 .
Using a variac apply impedance voltage at 16 raise
to the source (S) and load (SL) bushings. Raise the
voltage until rated current is read on the ammeter.
Impedance voltages may be obtained from the factory.
Contact your Cooper Power Systems representative
for assistance.
7 .
Let the regulator set in this condition for approximately
24 hours. This will drive the moisture out of the coil into
the oil.
8 .
De-energize the regulator and drain the oil.
.
Refill with new oil.
0 .
Perform an insulation power factor test after the regu-
lator temperature has stabilized to the ambient tem-
perature. The reading results should be lower than the
original test results.
WARNING:
Hazardous Voltage. This procedure
must only be performed on a regulator that has
been removed from service. Failure to comply can cause
serious injury or death.
VR-T224.0
WARNING:
Hazardous Voltage. When trouble-
shooting energized equipment, protective gear
must be worn to avoid personal contact with energized
parts. Failure to comply can cause serious injury or
death.
VR-T213.0
WARNING:
Hazardous Voltage. This procedure
must only be performed on a regulator that has
been removed from service. Failure to comply can cause
serious injury or death.
VR-T224.0
WARNING:
Hazardous Voltage. The regulator
will be energized with load current present for
the duration of the procedure. The regulator must be
placed in a protected area, preventing anyone from com-
ing in contact with the unit. Failure to do so could result
in injury or possible death.
VR-T226.0
WARNING:
Hazardous Voltage. The regulator
tank must be solidly earth grounded. Failure to
comply can cause severe personal injury and equipment
damage.
VR-T225.0
