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Anonymous Poster

Earthing-touch & step voltage

03/02/2008 11:53 PM

known soil resistivity ,number of electrodes to achieve 1 ohms,lay out of earth grid

how to calculate touch & step voltage ,any formula?

country india noble

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Power-User

Join Date: Oct 2006
Location: Kolkata, India
Posts: 447
#1

Re: Earthing-touch & step voltage

03/03/2008 3:45 AM

Do you belong to Electrical Engineering? If yes...study relevant books/docs. If No, its of no use for you.

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#2

Re: Earthing-touch & step voltage

03/03/2008 4:58 AM

Hello Guest,

Are you building a:

1. Power station

2. Substation

3. TV transmitter station

4. Radio Transmitter station

5. DC Transmision link - Sending

6. DC Transmision link - Receiving

Advise voltages of the installation, and whether AC or DC.

Advise expected Earth currents through the electrode/s.

Advise the ground area of the installation.

Advise type of 'soil':

  1. Swamp bottom
  2. Seawater surrounding peninsula
  3. heavy clay
  4. Shingle (gravel fill)
  5. Garden loam/silt
  6. granite outcrop
  7. Desert sand
  8. Other, specify please

There are further specifics needed, but the above should do as a starting point.

Looking forward to your reply, with thank you.

Kind Regards....

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Participant

Join Date: Mar 2008
Posts: 1
#4
In reply to #2

Re: Earthing-touch & step voltage

03/15/2008 7:15 AM

thanks for reply

it will be a 33kv sub station 9mva

soil is desert sand

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Guru

Join Date: Jan 2008
Posts: 1753
Good Answers: 59
#3

Re: Earthing-touch & step voltage

03/03/2008 6:44 PM

I do not care to repeat Sparky's questions, which are to the point.

I am not even willing to believe that the soil resistance is known, as it is seasonally dependent to say the least. And I bet, that nobody knows, what it will show after an 8 weeks of drought.

If it is a safety ground, you may have to go down to the ground water table level, and do something elaborate to maintain year around. Bonding it back to the main power panel is still absolutely needed.

If it is a sensor ground, it is a customary and idiotic specification, as modern sensors come in not grounded and isolated flavors. It is idiotic and selfdefeating, as soon as a power ground is installed nearby.

If it is Radio Frequency ground, a ground mat, not the DC value is the deciding factor.

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Power-User

Join Date: Oct 2006
Location: Kolkata, India
Posts: 447
#5
In reply to #3

Re: Earthing-touch & step voltage

03/17/2008 12:39 AM

You know why earth electrode is used in Earth Mat design? To get advantage over non uniform soil resistivity of earth layers. In software the 2-or 3 layer model can be created to get better calculation of earth resistance. Hence drought will nit affect if we use more and deeper electrode. In a project in middle east where soil resistivity if tremendously high, engineers used a wells quite deeper and inserted fe nos of electrode in few places. Alternatively a treated layer of soil can be used on earth and earth mat can be used. This concept is being used in many projects.

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Participant

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#6
In reply to #5

Re: Earthing-touch & step voltage

06/17/2010 3:21 AM

related to to touch & step voltage calculation, I had also met the following problem, anybody can help me.

our system as below: from upstream 34.5kV to our Transformer 35.5kV/13.8kV, the TR is grounded via 400A resistor. and LV transformer 13.8/0.48kV transformer will be ungrounded (Open neutral).

1. is this requested to calculate Step/Touch voltage for LV system? (is IEEE 80 applied for HV (> 1000V) system only?)

2. The requirement is "the higher of Line-Ground or Line-Line-Ground fault will be used for the step/touch voltage calculation". As I understood, the main element current through human body is Line-Ground fault, so Line-Ground fault should be applied. (so case of ungrounded system, no L-G current cause step/touch voltage)

3. In some requirement for GPR (ground potential rise) less than 300V for Telecommunication system, if the calculated GPR is higher than 300V, any solution for Telecommunication system?

any senior can help me, I will thank very much.

AnhTai

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