In preparing to take insulation resistance readings on a main generator, the windings should be grounded for about 15 minutes prior to the test. For what reason should this be done?
ā¢ Insulation resistance testing (megger testing) on generator windings ā¢ How electrical capacitance in long windings behaves after the generator is shut down ā¢ Why stored charge in windings can affect both safety and test readings
ā¢ Think about what happens electrically inside long coils of wire when voltage is removed. Do they instantly become completely uncharged, or can something remain? ā¢ Which of the options deals with an electrical effect rather than a mechanical or temperature-related effect? ā¢ If the goal is a safe and reliable insulation resistance reading, what needs to be cleared or stabilized before connecting the test instrument?
ā¢ Identify which answers are about temperature and which are about electrical charge ā¢ Recall that generator windings can act like a capacitor relative to ground ā¢ Ask: Before using an insulation resistance tester, what must be done to remove stored energy and avoid misleading readings or shocks?
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