[dilbert247365]

What are the pros/cons of high resistance grounding versus solid grounding and low resistance grounding? What is the preference for different applications? What complications does high resistance grounding introduce in drive system applications?

Thank you.

 

[Zog]

Thats an entire semester of an answer, have a more specific question?

Start here for the basics http://www.i-gard.com/Downloads/techlib/Public/Resistance Grounding Booklet.pdf

 

[someonespecial]

One main benefit of high resistance grounding is that if there is a ground fault, the equipment will still operate rather than trip out.

A quick example would be if you had a mission critical submersible sump pump in a grounded container. If the pump faulted in the water and energized the water, the OCPD might trip can cause a flood. If you have a high resistance ground system and have a fault, the equipment would continue to operate and there would likely be an alarm to alert personnel to the danger and that a repair needs to be made.

 

[Speedy Petey]

What are the pros/cons of high resistance grounding versus solid grounding and low resistance grounding? What is the preference for different applications? What complications does high resistance grounding introduce in drive system applications?

Thank you.

Home work? Or test question?

Either way, you tell us what you think then we'll discuss it.

 

[ponyboy]

We never covered high resistance grounding when I had my apprenticeship. Grounding and bonding could be a year course in itself with all it encompasses.

 

[butcher733]

I prefer low resistance grounding. Cutting the rod in half makes it much easier to drive down fully.

 

[Meadow]

I prefer low resistance grounding. Cutting the rod in half makes it much easier to drive down fully.

? YOu mean high resistance grounding?

 

[sparky970]

The paper mills I work at have high resistance grounds. You don't want the paper machines shutting down just because a motor fails. Especially if there is a redundant motor to take its place.

 

[brian john]

The paper mills I work at have high resistance grounds. You don't want the paper machines shutting down just because a motor fails. Especially if there is a redundant motor to take its place.

Just some wording in your post that need straitening out, if the motor fails you are shutting down, if one phase faults you will continue to run.

 

[kelleyss]

One EE told me the big advantage is limited short circuit current in phase to ground fault. Less explosion factor.

 

[BT Electric]

One issue I have found in paper mills that are pre 1960's is that many of the motor starters have 480V control voltage, usually just 2 phases from the starter to the push buttons in the control panel. Dangerous and not always marked clearly. On/off controls for pumps sometimes will not shut off when a high resistance ground is present on the phases used. Same for reversing starters.

 

[backstay]

One issue I have found in paper mills that are pre 1960's is that many of the motor starters have 480V control voltage, usually just 2 phases from the starter to the push buttons in the control panel. Dangerous and not always marked clearly. On/off controls for pumps sometimes will not shut off when a high resistance ground is present on the phases used. Same for reversing starters.

And I thought most old paper mills were 575V. May it's a northern thing?

 

[BT Electric]

Must be. The ones in the south all seem to be 480V.

 

[brian john]

One EE told me the big advantage is limited short circuit current in phase to ground fault. Less explosion factor.

Yes on the first fault the fault current is limited to somewhere (IN MY EXPERIENCE) to less that 12-25 amps. In an Unground system the fault current is "0" amps

 

[sparky970]

And I thought most old paper mills were 575V. May it's a northern thing?

They still have quite a bit of 480V controls at one of our sites. We converted about 40 starters to 120V a couple years ago. Changed out CPT's, coils, fusing, and added PLC controls. I think they would have been better off buying new buckets and starters. Of course they had us install I/P's and P/I's to integrate the pneumatics into the DCS.

 

[sparky970]

And I thought most old paper mills were 575V. May it's a northern thing?

The paper mills here have both