Millivolt drop testing on energized equipment

[Jhaemus]

Our company performs infrared inspections of electrical systems. If safe, we measure current using clamp-on meters. Recently, a customer asked why we don't measure millivolt drops and our response was we did not think that the added risk was worth the information gained. They informed us that another company takes millivolt readings from live circuits and includes them in their reports. From what little I know, you isolate the circuit and perform the test with a controlled power source. Is it safe to perform this test on un-isolated circuits?

 

[zog]

Well define "Safe". Just like with your IR scanning and clamp on readings you will need to waer the correct shock and arc flash PPE required based on either the tables (If they can be applied) or the arc flash label. But mV drop readings would fall under testing and T/S so it would be allowed but you need an EEWP (Which you should already have for what you are already doing).