MIL-HDBK-1025/10
voltage the person in charge of the testing should, in addition to other applicable
instructions in this handbook, take the following precautions:
a. Use only devices that have been checked and found to be properly calibrated
both immediately before and immediately after the test.
b. When testing live circuits or equipment, all temporary leads used in testing
should be securely supported to prevent interference with other workers or injury to the
tester. Protect testing personnel and others (particularly their eyes) from flashovers.
c. When performing mechanical tests, keep the operating personnel and others at a
safe distance or in a safe location by means of barricades, to prevent injury resulting from
the failure of the equipment being tested.
d. Use an approved voltage detector when testing for blown fuses on low-voltage
circuits. Do not use fingers as the test for blown fuses.
e. A test indicating absence of voltage on the secondary side of a transformer or
regulator should not be considered as a positive indication of the absence of voltage on the
primary side.
Switching Safety. Opening/closing a power switch may expose the
6.5
operator to some degree of hazard. An accident may occur if a switch is closed when a
fault is still present on the line. The supervisor, before writing the switching orders,
should prepare the switching sequence and all load isolation requirements. All switches
operated in the switching sequence should be correctly identified and the instruction
manuals of the switches should be provided. The worker should read the instruction
manual to be familiar with the switch operation. All safety steps listed in the instruction
manual should be followed before opening/closing a switch.
WARNING
Switches may fail during switching operations, creating arc blast
hazards. Wear fire resistant clothing and/or switching suits during
these operations in accordance with Table 11 distances.
6.5.1 Air Switches. Most switches today are airbreak switches. Many
switches cannot be opened if there is a load on the line, if there is a large transformer
magnetizing current from transformer, or if there is a heavy charging current from an
unloaded transmission line. Always know the interrupting capabilities of the switch you
are opening or closing.
6.5.1.1 Disconnect Switches. Disconnect switches of the nonloadbreak type will
not be used to interrupt loads and magnetizing currents, unless specific approval has been
given that the disconnect will interrupt the current safely or unless the switch is of the
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