Safety Precautions for Various Types of Apparatus
1-26 72A-1230 Rev. F
July 22, 2005
After the tests are completed, all test leads should be disconnected first from
the equipment terminals and brought down to ground level before they are
disconnected from the M4100 Instrument. The #6 copper test set ground
should be the last lead to be disconnected from the set.
WARNING Never attempt to disconnect the HV Test Cable or the Low Voltage cables
from either the terminals of the test specimen to which they are connected
at the outboard end, or from the receptacles on the M4100 instrument at
the inboard end, unless the M4000 VOLTAGE CONTROL is set to
ZERO, and the Operator's Safety Switch and the Extension Safety Switch
are both released. Attempts to disconnect leads while the M4000 is
energized may result in a serious, and possibly lethal, electrical shock.
Safety Precautions for Various Types of Apparatus
In addition to the items included in ”Safety Practices – General Rules”
on page 1-20, the following are specific considerations that have to do with the
testing of various types of apparatus:
Bushings When performing either single or multi-hot-collar tests using rubber Hot
Collars, be aware that the rubber collar is a conductor, and that it is at the test
voltage during the test.
Breakers Prior to any testing, steps should be taken to disable the breaker so as to avoid
inadvertent operation during testing. In a closed breaker test, both bushings
will be energized at test potential, and contact between the bushings and either
test personnel or test leads should be avoided.
When testing lift-rods, operating rods, or any component internal to the
breaker, the operating mechanism should be blocked, fuses removed, and any
other necessary measures taken to ensure that the breaker is inoperative.
Transformers 1. When performing bushings tests, the opposite windings should be
grounded.
2. When performing excitation tests, floating terminals should be considered
live.
3. Use caution when applying test voltages to a transformer from which the
oil has been removed. Recommended test voltages for testing a
transformer without insulating fluid are listed in the Doble Test
Procedures manual.
4. Under no circumstances should test voltages be applied to oil impregnated
insulation while the insulation is under vacuum.
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