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Section 1
An Introduction to Impulse Testing with the MegaPulse PF series tester
The impulse test is designed to simulate impulse surges which occur in everyday life due to nearby lightning strikes,
switching transients, and other high-frequency faults on the power distribution network. Impulse testing is the
fundamental method for empirical verification of the adequacy of insulation. Other methods of ensuring adequate
insulation (AC or DC Dielectric Withstand testing, measurement of over-surface creep age, through-air clearance, or
distance-through-insulation) are all extrapolated from the results of impulse testing. The impulse test is performed to
ensure that the insulation in question will be able to function properly when subjected to similar impulse surges in the
field
.
Safety Precautions
The impulse withstand test can generate voltages in excess of 2000V peak at potentially lethal current levels. Currents
of as little as 5mA at 120 volts can cause death; the MegaPulse can deliver currents of more than 3000 Amps peak for
very short time duration. The potential for serious injury or death exists and personnel should be aware when they
conduct this test.
Test Personnel
Personnel require special training to conduct the impulse test. They should understand electrical fundamentals clearly
and be aware that high voltage is adept and creative at completing a path to ground. Instructions should include a
warning against any metal jewelry. Operators should not allow others in the testing area, especially when tests are
being conducted. Organization is to be stressed. The operator should keep the area free of unused leads and equipment.
Testing Area
The area used for conducting the impulse test should be as remote as possible from normal production line activities.
Only personnel conducting the test should be allowed in the area, and it should be taped or roped off to preclude casual
entry by other employees. In addition, the area should be marked "WARNING - HIGH VOLTAGE TESTING" or the
equivalent to warn others of the nature of the testing taking place.
The bench being used should be non-conductive, and any exposed metal parts should be tied together and grounded.
If a conductive surface must be used, it should be grounded. Because of sparking during an impulse test failure, it is
not safe to conduct impulse testing in combustible atmospheres.
It is imperative that a good ground be provided to the MegaPulse tester. Before connecting the equipment, ensure that
the building wiring provides a low-resistance ground. If the MegaPulse tester is used on a high-resistance grounding
circuit, dangerous high voltages may be present to the operator. In addition, the power to the Testing Area should be
provided with an easily reached shutoff switch which can be actuated by personnel outside the Area if needed.
CAUTION:
Plug on power cord is disconnect device. The power to the Testing Area should be provided with an
easily reached shutoff switch
which can be actuated by personnel outside the area if needed.
