Megger 651403, Instruction Manual

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AVTM6514J Rev. A (03/2003)
19
Section 6
Operation
OPERATING PROCEDURE
Be sure to read and understand Section 2, Safety, before operating.
1. Ensure that the setup procedures detailed in Section 5 have been performed.
Remove the safety ground jumper from the cable under test.
2. Set the OUTPUT KILOVOLTS switch to ZERO START.
3. Set the ON/OFF switch to ON; the red POWER pilot lamp lights, and the fan
starts.
F
WARNING
The high-voltage output circuits have now been enabled and
high voltage will be present hereafter.
4. Set the OUTPUT KILOVOLTS switch to the first position (3 kV), and observe the
OUTPUT CURRENT meter. The Impulse Generator applies a 3 kV pulse every six
seconds to the cable under test; a significant deflection (at least 10 percent)
observed at these intervals indicates either a sparkover has occurred, or that the
cable has a short circuit. No deflection means the cable can withstand 3 kV.
5. If no sparkover occurs at 3 kV, set the OUTPUT KILOVOLTS switch to the next
step (6 kV) and repeat. If the cable withstands 6 kV, continue through the other
steps of the OUTPUT KILOVOLTS switch until sparkover occurs or the cable has
withstood several 15 kV pulses. The highest possible output for the Impulse
Generator is 15 kV; if there is no significant indication on the OUTPUT
CURRENT meter when 15 kV impulses are applied, the breakdown voltage of the
fault is greater than 15 kV.
6. To shut down, refer to "Shutdown Procedure."
INTERPRETING THE OUTPUT CURRENT METER
The most effective device on the Impulse Generator for detecting sparkover is the
OUTPUT CURRENT meter, which displays peak fault current. To interpret these
readings correctly, it is necessary to understand their meaning:
a. The meter is calibrated to produce full scale (approximately 100 percent)
deflection with a 15 kV impulse into a short circuit. The reading is lower than