Phse ground current of Resistance grouding system

60,000V / 1.73 = 34,641V
34,641V / 10 Ohm = 3,464 Amps.
Are you sure of the resistance value?
What does the fault level on a 30kV bus have to do with a 60kV/5.5kV system?

Bill
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"Why not the best?"
Jimmy Carter

Hi Bill,

Sorry I was in a hurry yesterday and made mistakes.

The 60kV system neutral grounding resistor (NGR) is rated 200A 1s.

And the maximum fault level on the 60kV bus is 25kA.

We will use program such as ETAP to calculate grounding potential rise, step potential, touch potential, grouding resistance etc. what is the phase ground short circuit current that should be used? 200A OR 25kA?

Is the 60kV system ground fault limited to 200A by NGR?

Thanks,

Parkpower

Is the 200A NGR the only ground source on the 60 kV system?

The 10 Ohm rating of the NGR is what determines the ground current. The 200A 1s rating just means that the resistor will probably fail quickly. It is possibly meant for use on a lower voltage system. 3.5 kV rather than 60 kV

Bill
--------------------
"Why not the best?"
Jimmy Carter

If the 60/5.5 kV Transformer is star connected on 60 kV side and this neutral resistance is connected between star point and Grounding Grid
the short-circuit current through this resistance will be not more than 200 A.
The short-circuit current you have to take into consideration is 25 kA as it is supplied by 60 kV Network [Utility], [if the transformer is located on your yard].

if it is a 10ohm resistor on grounded neutral on a 60kv system than i agree with waross posts. U are limiting LG current to approx 3500Amps.

7anoter4 could u pliz explain how ur limiting avaib. ground fault current to less than 200A?

"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic — and this we know it is, for certain — then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". – Nikola Tesla

If the 60kV system has other ground sources such that the available ground fault current is 25 kA, what is the purpose of the NGR at the station?

Two points.
1> The available fault current is often less than the actual fault current. Available fault current is an easy to use and easy to determine value that is used to select properly rated switchgear and other components. Switch gear, fuses, breakers and any thing else that is rated in available fault current has actually been tested at the higher current levels that will normally be experienced under fault conditions.
2> Available fault current is usually phase to phase current.
If the system is properly grounded through a Neutral Grounding Resistor then the ground fault current will be limited by the NGR.
If you have a 10 Ohm NGR on a 60kV system, we really need a diagram to help you any more. There is a good FAQ on posting pictures.

Bill
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"Why not the best?"
Jimmy Carter

First of all I have to apologize as I saw "10ohm" as "100ohm". [I think a new pair of spectacles has to be considered!]
Second: I took the 60 kV system as High Voltage System [as 110 kV, for instance] so was to be grounded.
Further, I think, is not interesting how was the calculation way-a bit complicated for a 4 equations with 4 unknown parameters, in complex.
But now I agree, of course, with waross: you have to employ other star grounding resistance, in any case. In the case of an ungrounded system the double ground fault current is the considered current for GPR, Touch and Step Potential.
If, nevertheless, it is a grounded system, a single phase [homopolar] current has to be calculated and compared with double grounding.
In my opinion the Ik2- for double grounded fault- will be 20 kA and Ik1 from 14 to 25 kA depends-namely- upon Grounding Grid Resistance.