bring the insulated wire to the vicinity
of, but not connected to, the test set.
e. If the test set being used does not
have a built-in potential transformer for
high-side metering, a separate potential
transformer should be used to provide
f. Check accuracy of test set indicating
voltmeter by comparing it to a calibrated
voltmeter connected to the high-side
g. Adjust spherical gap oil test set to
flash over at the specified test voltage,
as calculated from charts. Then
energize the test set without connecting
it to the stator-winding phase to be
tested. Raise voltage until gap flashes
over, noting reading of test-set
voltmeter to verify reasonable
agreement and that voltmeter scale and
potential-trans-former ratio are correct.
Some tests sets are not equipped with
a spherical gap, so a separate
spherical-gap voltmeter should be used
in conjunction with these sets.
h. With the test set deenergized, adjust
the spherical gap to flash over slightly
above the required test voltage. This will
provide protection in the event of a test
set malfunction resulting in higher
i. Connect the test set to both ends of
the stator winding phase to be tested.
j. Energize the test set and raise the
voltage smoothly until the mark on the
test set indicating voltmeter is reached.
The rate of rise should be such that the
test voltage is achieved within 1 minute.
Care should be exercised so as not to
overshoot the test voltage. This voltage
should be held for 60 seconds. The
voltage should then be lowered smoothly
to zero in approximately 1 minute.
k. Repeat steps 3, 4, 9, and 10 for the
other phases to be tested.
60. Induced-Potential and Impulse
- Factory tests on new transformers or
regulators may include (a) 120- to 400-Hz
induced-potential test and (b) reduced full-
wave, chopped-wave, or full-wave impulse
tests. These tests require special equipment
and are not performed in the field, and will not
be covered in this bulletin. The standard 60-
Hz high-potential test, however, are simple to
perform and require only a transformer of
suitable voltage and capacity, with current
limiting equipment and means for controlling
and measuring the output voltage.
61. Voltage Values for AC Tests.-
potential, ac tests, if used in the field, should
be performed in accordance with Standard
Techniques for High- Voltage Testing, IEEE
Standard No. 4, 1978, or its latest revision.
The test voltage values to use are shown in
table F. All values in the table apply to 1 -
minute application of 60-Hz test voltage
applied between winding and ground, for
clean, dry windings at a temperature not
below room temperature and preferably not
C. The data given in table F under
"Periodic field tests on equipment in service"
are manufacturers' recommendations, as no
ANSI standards have been adopted for this
purpose. The high-potential test voltage
values for use on power cable vary with a
number of conditions and should be obtained
from the current cable standards. The
capacity of the high-potential test set (in
kilovolt amperes required to test generator
stators of various ratings) is shown in
(FIST 3-1 12/91)