🔍 Key Concepts

• Safety when using a megohmmeter (megger) on electrical equipment • Relationship between test voltage and the equipment’s normal or rated (exposure) voltage • Whether insulation resistance tests are done on energized or de-energized circuits

💭 Think About

• Think about what could happen to the megohmmeter and to personnel if you connect it to an energized circuit—what is the basic safety practice before working on most electrical equipment? • For an insulation resistance test, do you want the applied test stress to be higher, lower, or equal to the normal operating voltage in order to reveal weaknesses in insulation? • What is the purpose of insulation resistance testing: simply seeing if it works at normal voltage, or proving a margin of safety beyond normal operation?

✅ Before You Answer

• Confirm whether standard practice is to perform insulation resistance testing on de-energized equipment • Check typical insulation test voltage recommendations versus the equipment’s rated (exposure) voltage—are they usually higher, lower, or the same? • Verify which answer choice combines both: correct equipment condition (energized/de-energized) AND appropriate relative level of test voltage (equal/greater vs. less).