I am looking for Standard or Equation of calculation 500kV

The specification pertains to the surface voltage gradient of a bare overhead conductor in kV/mm. The other part is Radio Influence Voltage (RIV) in microvolts at a frequency of 1 megahertz at a voltage of 10% above the nominal phase to ground system voltage. The RIV test parameters are standard and the test is covered in North America by NEMA Standard 107, "Methods of measurement of radio influence voltage (RIV) of high-voltage apparatus". That standard will either be used directly in IEC or IEC will have an equivalent.

The conductor surface voltage gradient calculation depends upon the conductor diameter, whether it is single, bundled, single phase, three phase, conductor height above ground, etc. Several manufacturers in the US also manufacture Gradient Calibrators. One of those manufacturers is FCI-BURNDY and the EHV section of their catalog includes the standard formulae for determining the voltage gradient as well as a nomogram for finding average conductor surface voltage gradient. You can access that catalog at http://www.burndy.com.

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Basic equation is

S = KV / X Log e [r+t] / r

S= stress at any point P in the dielectric expressed as KV/cm

X= distance in cm from center of conductor to point P

r= radius of conductor

t= thickness of dielectric

KV = potential difference across dielectric in KV

The above formula assume homogeneity of the dielectric between the surfaces across which the electrical potential is applied.

Thank you for your helping,

But I have a following matter

If wire is bare conductor (mean is not dielectric such as PVC or XLPE...) and then how to find value of specification t " thickness of dielectric".

Refer to my previous reply but, following is an example of the calculation for a single phase, single bare conductor centered horizontally h centimeters above a horizontal ground plane.

Es = V / r ln (2h/r)

Where Es = Average gradient on the surface of the conductor (kV/cm)

V = Line to ground voltage

r = radius of the conductor (cm)

h = distance from the centerline of the conductor to the ground plane surface (cm)

The Maximum surface voltage gradient (Em) occurs on the side facing the ground plane and can be calculated by:

Em = h/h-r x Es

Thank you very much for yours helping.

I can calculate Maximum stress at surface of flexible conductor.

Can I ask you a question? what IEC standard have these equations.

thanks.

You might find the equations in an IEC standard but I doubt it. Log onto the IEC website and look through the standards.

I don't know your background, but most graduate EEs with a Power Option should be able to develop the equations. They can also be obtained from Electrical Engineering textbooks and handbooks (Standard Handbook for Electrical Engineers, Fink and Beaty, McGraw-Hill, for example) as well as numerous other sources.

More important than the equations is an understanding of how they are developed, applied, and the significance of the results.