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Anonymous Poster #1

Genset Earthing

05/29/2011 5:43 AM

Dear Members,

What are the factors to consider for earthing a generator set. what calculations are involved in sizing the earth cable?

Should the small mobile gensets for households be earthed?

Pls explain these set duty terms and their applications:

ESP, prime, continuous

regards

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#1

Re: Genset Earthing

05/29/2011 7:25 AM

Every equipment, if it is not rated as Class II or received power from low voltage isolation transformer. Then, it should be earthed.

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#2
In reply to #1

Re: Genset Earthing

05/29/2011 9:04 AM

Having worked on 660V 3MW systems that are earth free I'd take issue with that.

You can't just make general statements, for most situations you would be right but not all!

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#4
In reply to #2

Re: Genset Earthing

05/29/2011 9:24 AM

Show me that, TonyS. I have never seen any electrical equipments unearthed except class II. You are from England, you may know very well about PAT.

Depend on the situation and depend on what I really know, I don't have time to give the details as much as possible. The OP will understand it himself. You stated that 660V and 3MV, it is also so general, I cannot understand what is that. I also don't want to see the fights against each other here. That is not my purpose.

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#5
In reply to #4

Re: Genset Earthing

05/29/2011 10:27 AM

Simple it's a lot of power that is not earthed.

I only worked on it for 12 years and redesigned the power regulation. I think I know it exists.

And by the way it's 3MW

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#6
In reply to #4

Re: Genset Earthing

05/29/2011 10:44 AM

You've upset people on this site this weekend, you say you don't want to start arguments. You've a bit of bridge building to do!

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#7
In reply to #4

Re: Genset Earthing

05/30/2011 1:55 AM

I don't have time to give the details as much as possible. The OP will understand it himself.

Got to disagree with that bit of your post.... looking at the question and moreover, understanding the question, it would seem that if the OP did understand "earthing" then he would not be asking the question, so as TonyS says" You can't make general statements".....generalising is another way of saying something without any substance.. politicians do it all the time

As for PAT.. do you mean "Portable Appliance Testing"? Pray tell, what does PAT have to do with earthing of a generator? Last time I checked a 3MW gen set is not that portable!

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#8
In reply to #7

Re: Genset Earthing

05/30/2011 2:55 AM

Just put big enough wheels on it! (Aggreko may already have some that big.) But dangling a grounding chain off it probably won't be good enough.

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#9
In reply to #8

Re: Genset Earthing

05/30/2011 4:14 AM

Yes... and a towing hitch on your truck and away you go!!

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#10
In reply to #9

Re: Genset Earthing

05/30/2011 5:42 AM

Who say's it's not portable, last I heard it had moved from the UK to Spain. Took a bit of shifting by all acounts

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#11
In reply to #10

Re: Genset Earthing

05/30/2011 5:49 AM

the grounding chain.. perchance an anchor??

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#13
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Re: Genset Earthing

05/30/2011 9:07 AM

Just hope it took it's UK pension papers with it, it's old enough.

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#16
In reply to #1

Re: Genset Earthing

05/30/2011 10:58 AM

@ hien

I am a beginner only so Can you please explain class 2 in somewhat more detail so that i can read well from net or refer some book for further studies..

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#17
In reply to #16

Re: Genset Earthing

05/30/2011 11:09 AM

Ok, it is implying portable electrical equipments in term of safety level. Class II means the electrical equipments which have two classes of insulation. The first one is called basic insulation (like motor windings), the second one is called double insulation (like plastic cover).

So, we will have many class II equipments such as drilling machines... But remember that they belong to the portable equipments only. Since the definition of Portable equipments are very wide and the OP asked for household generator. In a certain aspect, it can be considered as portable one. That is why I posted my answer.

Hope it helps.

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#18
In reply to #17

Re: Genset Earthing

05/30/2011 11:17 AM

Thanks a ton..

Now I can build up my concept on the information you provided.

With Warm Regards,

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#3

Re: Genset Earthing

05/29/2011 9:08 AM

i) Zero sequence impedance of the generator, maximum permissible earth fault current magnitude & duration, etc.

ii) Yes! More so, with hosuehold gensets, where the danger of electrocution is more prononced as non-technical people ca and will handle electricity.

iii) ESP - Electroststic Preceipitator (or) Electrical Standard Products (or) Extra Sensuory Perception

iv) Prime & Continuous mean the same.

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#12

Re: Genset Earthing

05/30/2011 7:23 AM

Yes, the earthing of standby and other private generating plant (including portable and mobile generators) is necessary to protect against indirect contact that may result in electric shock. The objective is to create a zone in which voltage between exposed conductive parts get minimized in the event of an earth fault.

Various factors like generator per unit impedence, fault current levels, system criticality, duration of fault current, etc.

Approximate resistance to earth of Metal plate can be calculated from:

R = ρ/A ( π/A) Ohms.

Where, ρ = resistivity of soil in Ohm-meter and A = area of both sides of plate

Resistance of rod or pipe electrode is given by,

R = 110ρ/2πL*(loge 4L/d) Ohms

Where,

L = Length of rod or pipe (in cm),

d = diameter of rod or pipe in cm and

ρ = resistivity of the soil in Ohm-meter.

May be this will help you.

Sure answers always...

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#14
In reply to #12

Re: Genset Earthing

05/30/2011 9:18 AM

Verbal diarrhoea.

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#15
In reply to #14

Re: Genset Earthing

05/30/2011 9:21 AM

give him a break..he's a newbee!!

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#19

Re: Genset Earthing

05/31/2011 4:02 AM

British Standard 7671.

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A.Classy.Lass (2); Anonymous Poster (1); brich (4); electricalexpert65 (1); hien.nguyenquoc (3); PWSlack (1); TonyS (5); Tornado (1); Vinu_Answers (1)

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