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Author Topic: Generators  (Read 17027 times)

BobWitte

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Re: Generators
« Reply #40 on: November 25, 2013, 05:38:02 pm »

I should have some time to re-read this article by the weekend. Thanks for reminding me.


Just wondering if at some point the original thread idea of proper generator grounding can come back to life and the discussion of several papers that had links posted? (page 2 of the thread).


Generators/Ground Rods/ etc.  We do 5 outdoor shows a year and the local city Parks Department provides a portable diesel generator and a portable stage (trailer that opens up....). Two Hubbell "Kellems" are provided that are fed from the generator with multiple GFCI protected 20 amp circuits. A ground rod is never used. The guys that set the generator up know very little about it and or safety.... I do always check voltage and grounding (safety/neutral) and now will be using a Volt Alert too - especially after seeing the condition of some of the gear that musicians use. We have had some false GFCI trips (maybe due to several power strips that, based on reading here, may have surge protection MOV's that the leakage current could be an issue).


Thanks


Bob







Jonathan Johnson

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Re: Generators
« Reply #41 on: November 25, 2013, 11:50:44 pm »

Without re-reading the entire thread, I can't remember if this has been discussed.

Consider this scenario:
  • Generator is not provided with a ground rod
  • Equipment with a grounding conductor is powered by the generator
  • Other equipment with a grounding conductor is powered by installed circuits ("shore power")
  • The variously-powered equipment is connected by an audio interconnect with a shield that's connected at both ends

At this point, the shield of the audio interconnect becomes the sole connection between the ground of the generator circuit and the ground of the shore power.

What is the implication? Does this pose a potential threat to either personnel or equipment? What kind of fault could cause excessive current flow through the shield resulting in melting or fire? What kind of fault could cause electric shock?

It seems to me -- and I have not studied this in an engineering fashion -- that where there is potential to power interconnected equipment from disparate sources, it would be wise to connect the grounds of those sources in some fashion. However, I would be concerned that connecting those grounds could result in large ground currents in the cross tie.
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Lyle Williams

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Re: Generators
« Reply #42 on: November 26, 2013, 03:24:28 am »

Without re-reading the entire thread, I can't remember if this has been discussed.

Consider this scenario:
  • Generator is not provided with a ground rod
  • Equipment with a grounding conductor is powered by the generator
  • Other equipment with a grounding conductor is powered by installed circuits ("shore power")
  • The variously-powered equipment is connected by an audio interconnect with a shield that's connected at both ends

At this point, the shield of the audio interconnect becomes the sole connection between the ground of the generator circuit and the ground of the shore power.

What is the implication? Does this pose a potential threat to either personnel or equipment? What kind of fault could cause excessive current flow through the shield resulting in melting or fire? What kind of fault could cause electric shock?

It seems to me -- and I have not studied this in an engineering fashion -- that where there is potential to power interconnected equipment from disparate sources, it would be wise to connect the grounds of those sources in some fashion. However, I would be concerned that connecting those grounds could result in large ground currents in the cross tie.

A pivotal issue is whether the generator neutral is tied to ground.  I'd expect that to be the case with large gensets, but the situation with small ones is uncertain.

A large genset may get a lower impedance path to ground through it's skids than the token earth rod driven 2' into the soil.
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Re: Generators
« Reply #42 on: November 26, 2013, 03:24:28 am »


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