MIL-DTL-24640C
(2) A source of DC voltage which can be adjusted to the specified magnitude (see 3.1), and which shall
have the capacity to provide an electrical current of not less than ¼ A. This source shall incorporate an overload
relay which shall reduce the source voltage to zero whenever an applied load (that is, the specimen, see 4.8.6.3)
attempts to draw electrical current to exceed this current capacity.
b. When required, a water tank, which shall be filled with water and shall be of sufficient size to contain the
4.8.6.3 Procedure. The voltage source shall be electrically connected to the specimen as specified [see (a), (b),
(c), (d), (e), (f), (g), (h), and (i)]. For each connection, the test voltage from the voltage source shall be increased, in
a uniform manner, from 0 V to the specified voltage (see 3.1) during a period of not more than 60 seconds or less
than 10 seconds, except that specified voltages of less than 600 V may be applied instantaneously. (This gradual
voltage application is generally necessary to prevent a current in rush, and the consequent tripping of the voltage
source overload relay caused by specimen capacitance.) This specified voltage shall then be maintained for a period
of 1+½, -0 minute (unless the voltage source overload relay trips, see 4.8.6.4); following which the test voltage shall
be reduced to zero at approximately the same rate at which it was applied.
a. Conductor to ground (cable, one conductor, unshielded, jacketed). Specimens incorporating a single
insulated, jacketed conductor without shield or armor shall be tested to water. The specimen shall be submerged,
except for its extreme ends (which shall remain exposed to the air), in the water tank for a period of not less than 1
hour. Following this, and while the specimen is still submerged, the specimen shall be tested as follows. The single
conductor shall be electrically connected to one terminal of the voltage source. The other voltage source terminal
shall be electrically connected to the water surrounding the specimen (as by means of a bare metal wire which is
both connected to the voltage source terminal and suspended within the water surrounding the specimen). The
voltage withstand test shall then be performed as specified.
b. Conductor to conductor (cable, unshielded, jacketed). Used for cable types incorporating two or more
insulated conductors (such as singles, pairs, or triples) with no individual or overall shield: one insulated conductor
shall be selected and electrically connected to one terminal of the voltage source. All other conductors within that
transmission line shall be electrically connected to the other voltage source terminal. The voltage withstand test
shall then be performed as specified. In a similar manner, the voltage withstand test shall be performed between
each remaining conductor within the selected transmission line and the short circuited combination of all other
conductors within that transmission line. Following this, and in an identical manner, the voltage withstand test shall
be performed on all remaining transmission lines within the specimen.
c. Conductor to conductor with overall shield (cable, overall shielded, jacketed). Used for cable types
incorporating two or more insulated conductors (such as singles, pairs, or triples) with no individual shields and with
an overall shield: one insulated conductor shall be selected and electrically connected to one terminal of the voltage
source. All other unshielded insulated conductors and the overall shield shall be electrically connected to the other
voltage source terminal. The voltage withstand test shall then be performed as specified. In a similar manner, the
voltage withstand test shall be performed between each remaining insulated conductor within the specimen and the
short circuited combination of all other insulated conductors and overall shield.
d. Conductor to conductor with component shield (cable, shielded components, overall unshielded, jacketed).
Used for cable types incorporating one or more individually shielded, insulated conductors: one insulated conductor
shall be selected for measurement, and shall be electrically connected to one terminal of the voltage source. All
other insulated conductors within the component and the shield shall be electrically connected to the other voltage
source terminal. The voltage withstand test shall then be performed as specified. Following this, and in an identical
manner, the voltage withstand test shall be performed on all remaining insulated conductors within the component.
After the completion of this component, this procedure shall be repeated for all other shielded components within
the specimen. The cable shall then be tested for component shield voltage withstand [see (g)].
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