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Kalyan74
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Join Date: Mar 2010
Posts: 7

Substation Grounding Design

03/22/2010 12:01 AM

Hi,

Can anyone tell me about easiest way of calculating fault current level (worst case) for designing a ground grid for a typical 400 kV Transmission Substation? Any thumb rule for it ???

Is fault current from lightning stroke need to be incorporated in this design? There is no mention of it in IEEE design manual.

How to determine the worst case scenario for designing substation ground grid?
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ikhanuk
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Join Date: Aug 2009
Posts: 91
#1

Re: Substation Grounding Design

03/22/2010 4:20 AM

hi

you can use the available upstream short circuit MVA from utlity data or

or u can also use 1000 MVA OR 500 MVA as initial guess depend on the system capacity

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PWSlack
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#2

Re: Substation Grounding Design

03/22/2010 9:16 AM

There is no way to quantify the current in a lightning bolt. When it happens, it is there for only a very short time.

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Indhs
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Join Date: Feb 2010
Location: Australia
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#3

Re: Substation Grounding Design

03/30/2010 5:19 AM

Hi,

I think its best you stay away from designing a ground grid for a 400kV substation.
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Kalyan74
Member

Join Date: Mar 2010
Posts: 7
#4
In reply to #3

Re: Substation Grounding Design

03/30/2010 4:43 PM

Why is so? What does that mean? Does no one do it? Really discouraging!!!
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Indhs
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Location: Australia
Posts: 13
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#5
In reply to #4

Re: Substation Grounding Design

03/30/2010 7:28 PM

The question you ask suggest this is the first time you are attempting to design a grounding system. If you are attempting a course work, then by all means ask anything, there are no silly questions. If you are designing for a "real" project then you should attempt under the guidance of an experienced engineer.
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rajukailas
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Join Date: Dec 2009
Posts: 14
#6

Re: Substation Grounding Design

04/02/2010 9:03 AM

Dear Sir

You can design the earthmat for the substation. Not a Herculean task. you can refer IEEE 80 and IEEE81 for the design.

Fault level of the station can be calculated using softwares like Neplan or Digscielent etc.

If those are not available collect fault levels of upstream stations. then calculate the fault level of new station considering the impedance of the line.

regards

raju
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Kalyan74
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Join Date: Mar 2010
Posts: 7
#7
In reply to #6

Re: Substation Grounding Design

04/04/2010 7:35 PM

Hi Sir,

Could you tell me whether we have to take into account for the impedance of the power transformer (inside the substation) also, but as per IEEE 80 std, it is a local source. But, fault from remote source needs to be considered with high priority.I am not sure whether I have to add the impedance of these both items as well.

Do we need to take account the fault current arising from lightning strokes as well?

Could you plz clarify this.

Thank you.
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rajukailas
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Join Date: Dec 2009
Posts: 14
#8
In reply to #7

Re: Substation Grounding Design

04/05/2010 1:08 PM

Dear Sir

Lightning is not considered for earth mat design.

The transformers of substations are normally fed from other stations or generating stations. That means source is incoming line. Consider a 110/11kV SS. Here the 110kV of the transformer is fed from 110kV bus.which in turn is fed from a remote station. So the fault level of 110kV bus is the highest one in the substation. In the case of a 110kV bus fault(The largest fault) transformer impedance is not coming into picture.So you need not consider this impedance.

If you want to calculate the fault level of 11kV side you have to consider this. But this will be lower than the fault level of 110kv bus.

For designing earth mat we must take the highest fault level of the substation.here 110kV fault level.

regards

raju
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bishwajit_saha
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Join Date: Aug 2010
Posts: 8
#9
In reply to #8

Re: Substation Grounding Design

01/21/2011 11:48 PM

Best Answer
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Users who posted comments:

bishwajit_saha (1); ikhanuk (1); Indhs (2); Kalyan74 (2); PWSlack (1); rajukailas (2)

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