VLF / hipot tester

A VLF hipot is a portable high-voltage AC source that runs at very low frequency. It is used for withstand testing of shielded medium-voltage cable systems, including the cable, splices and terminations. IEEE 400.2 sets VLF AC testing in the range 0.01 Hz to 1 Hz. Typical sets output 0.1 Hz down to 0.01 Hz and are rated by the load capacitance they can drive. Because the frequency is so low, testing a long cable needs much less power than a 60 Hz supply: about 600 times less at 0.1 Hz. Common uses are acceptance tests on newly installed or repaired cable before it is energized, such as in wind and solar underground AC collection systems. With extra measuring equipment, the set also acts as the voltage source for diagnostic tests such as tan delta and partial discharge. A withstand test is meant to drive severe defects to failure. Do not use it when you cannot accept a cable failure; diagnostics at or below operating voltage can be non-destructive. Many owners limit VLF to operating voltage for a few minutes as a proof test. Take test voltages from IEEE 400.2, and repair and retest any circuit that fails.

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• sentence 1: support check: partial - Passages cover VLF AC source, low frequency, withstand testing and cable/splices/terminations, but "portable" is stated (quite portable) while "shielded medium-voltage" is only implied via MV class and the IEEE shielded cable guide title; mostly supported with minor gaps.
• sentence 4: support check: partial - Acceptance/testing of new or repaired cable before reenergizing and wind farm cable are stated, but solar underground AC collection systems are not mentioned.
• sentence 4: review: partial - Testing newly installed or repaired cable before reenergizing is stated, and wind farm cable testing is named, but the quoted text never mentions solar underground AC collection systems; that appears only in a source ID. -->