Dear Professor, Scientists and Technicians in the field :
I'm trying to compute the Charging Current for a particular distribution Overhead line (25 or 35 kV).
And I found a paper where I found a couple of equations which allows you to calculate it.
However, in both of the equations you need to know the value of the Capacitance; between the line and the Ground
(in the attached image the equivalent electric circuit of this can be seen)
Two different circuits are shown here (a & b), because the paper where I took that, gives two different sub-methods to calculate the Charging Current of the line. Bith in both the Capacitance is needed.
I have no clue how to be able to figure out the value for the Capcitance.
Does anyone know about this subject ?
By the way, the formula for the Charging Current which appears in this paper is :
I = omega * C * [ V_phase-phase / sqrt(3) ]
I will really thank if someone can help
Regards !
PS. Paper attached too
Hi Franklin Uriel Parás Hernández ,
this recently published paper seems to present a review on measurement techniques applied to the line-ground capacitance, and will probably contain a section on calculation, too:
Article Three-phase and single-phase measurement of overhead power l...
Franklin Uriel Parás Hernández The capacitance of a power distribution overhead wire between phase and ground may be calculated using the formula:
C = 2 * π * ε * L / ln(d / r)
Where: C = capacitance (in farads) ε = relative permittivity of air (approximately 8.85 x 10^-12 F/m) L = length of the line (in meters) d = distance from the line to the ground (in meters) r = radius of the conductor (in meters)
Once you have estimated the capacitance, you can use it in the formula for the charging current:
I = ω * C * [V_phase-phase / sqrt(3)]
Where: I = charging current (in Amperes) ω = angular frequency (2 * π * f)
f = frequency of the AC power (in Hz)
V_phase-phase = voltage between two phases of the line (in Volts)
Please keep in mind that these are only estimates, and the real capacitance will vary depending on factors such as the shape of the conductor, the height of the line above ground, and the presence of other adjacent conductors or buildings. To obtain a more precise measurement, simulation software or field experiments are advised.
Dear Joerg Fricke :
Thank you for the paper. It contains useful information.
Dear Qamar Ul Islam :
Thank you for your kind answer; I think I can use the procedure that you mentioned.
One question on the first formula:
with "r = radius of the ocnductor", do you mean the metallic conductor (withouth any of the insulation layers) ?
Or do you mean the radius of the whole cable ?
Thank you,
Dear Qamar Ul Islam
I sent you and Inbox.
Would you allow me to talk you about the formulas you shared on this ?
I'll appreciat it much:)
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