How do you calculate the capacitance between earth and a transmission line wire? - Page 1
Forum section: electronics / beginners

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: August 01, 2023, 01:49:34 pm
content: What would be the area of the wire used for the calculation? would it be the circumference? Would it be half the circumference? would it be the diameter of the wire?And what about between 2 round wires? what would be the area used for calculating the capacitance then?

author: TimFox
author_rank: Super Contributor
timestamp: August 01, 2023, 04:39:52 pm
content: Standard reference works, such as “Reference Data for Engineers” have both equations and geometry diagrams for all the common configurations of wire and cable transmission lines, and surely you can find this information online. I’m away from my home library for another day.

author: Terry Bites
author_rank: Super Contributor
timestamp: August 01, 2023, 05:06:27 pm
content: A single conductor suspended above ground?www.microwaves101.com/encyclopedias/wire-over-ground-transmission-lineThis calculator work on the exometric region, possibly Canada too.

author: Jwillis
author_rank: Super Contributor
timestamp: August 01, 2023, 09:17:29 pm
content: Check this out. It might help.https://circuitglobe.com/capacitance-of-transmission-line.html

author: MathWizard
author_rank: Super Contributor
timestamp: August 02, 2023, 01:40:26 am
content: So if I'm using or understanding the equations right, if you had a 1cm diameter wire carrying 60Hz, 6m/~20ft above the ground, with air in between, you would have 467Ohms of reactance. So thats 5.7uF, I did the math wrong, it's not 1.24F.So it isn't big, but that's per meter tho right ?

author: Terry Bites
author_rank: Super Contributor
timestamp: August 03, 2023, 08:51:49 am
content: I think at 5.7uF/m the power company would be in very deep sh** !Redo the math and watch your units.

author: MathWizard
author_rank: Super Contributor
timestamp: August 06, 2023, 07:54:01 pm
content: I used Zo=(60Ln(4*height/dia))/SQRT(relative permittivity of air) , with meters, and got 467 ohms reactance, and so said at 60Hz thats 5.7uF. So what should it be ?Seeing how they don't mention length, that's why I figured its per length somehow. That would be a lot of capacitors tho, going from house to house.

author: johansen
author_rank: Super Contributor
timestamp: August 06, 2023, 08:11:54 pm
content: 450 ohms does not sound far off. However that does not directly translate into a bulk capacitanceRead herehttps://en.m.wikipedia.org/wiki/Characteristic_impedance

author: TimFox
author_rank: Super Contributor
timestamp: August 06, 2023, 08:12:48 pm
content: For a lossless transmission line,Z0= (L/C)1/2, whereLandCare the inductance and capacitance of the line per unit length (feet, meters, furlongs--it cancels out) --notthe value ofXCin an arbitrary length.

author: MathWizard
author_rank: Super Contributor
timestamp: August 06, 2023, 11:25:31 pm
content: Well whats this for then ? I'll read some more of it. I started going over the physics chapters on electricity and magnetism again, I'm sure some stuff like this will come up.https://www.microwaves101.com/encyclopedias/wire-over-ground-transmission-line