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 MIL-HDBK-1023/4
b) High-voltage impulse waveforms and resultant current pulses create special safety
problems. A large, rapidly changing current, even across small values of impedance, can
generate dangerous voltage levels. The test set design provides two distinct ground systems - the
apparatus case ground and the surge ground. The apparatus case ground, which must be
connected to a good local ground, is designed to protect the operator by preventing a difference
of potential between the apparatus case and the ground in the immediate vicinity. The surge
ground is designed to return the impulse current back to the capacitor. This surge ground lead is
a continuation of the output cable shield and should not be extended.
c) On termination of a test, even after power has been removed from the test set,
energy can still be stored in the capacitor bank and cable. For this reason, a manual ground is
included in this equipment. The voltmeter resistor will gradually reduce such stored energy to a
safe, low level. Then the manual ground must be closed to place a direct short circuit across the
capacitor bank and the cable under test. It is recommended that, before removal of the test set, a
ground bond be placed across the cable under test and remain in place until access to the cable is
again required.
d) If the test set is properly operated and all grounds correctly made, no rubber gloves
are necessary. As a routine safety procedure, however, some sites require the use of rubber
gloves not only in making connections to the high-voltage terminals but also in manipulating the
controls. This is an excellent safety practice.
Figure 8
Typical Impulse Generator/Proof Tester
4.8
Acoustic Detector
4.8.1
General
a) The acoustic detector, Figure 9, is a unique instrumentation system designed to
detect the intensity of pulsed sound waves in the earth. It is primarily used with impulse
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