Magnetic Field Calc

[mivey]

Yes, completely sure. We need to achieve 0.4 uT (microTesla) at 50m from the center of the line.

This can be fairly easily achieved by phase configuration. For example, using 800 kV spacing, 2000 amps (1000 per side), and rolling from

A-A
B-B
C-C

to

A-C
B-B
C-A

gets me around an 85% magnetic field reduction at 50m (0.643 uT went to 0.098 uT).

Putting in a return ground made the field less under the line but slightly higher at the 50m point (0.861 vs. 0.643 uT unrolled and 0.115 vs. 0.098 uT rolled).

It is also interesting to look at what happens when one side of the structure feeds power in a different direction from the other side (say for a loop feed in and out of a substation).

It is kind of sad that they don't show the calculations anymore, instead they offer a sort of software now.

software came with both editions.

Anyway, I think I can figure it out from here.

Thanks.

No problem. Have fun.

 

[mivey]

Mayimbe,

It just occurred to me that they may have seen a reduction in the magnetic field at the 1 meter measuring height when they added the return wires only because this raised the tower configuration. Elevating the phases is what caused the far field reduction, not the added return conductors.

As I stated in the prior post, much better results will be obtained by re-configuring the phases (and you won't have to spend money on taller towers and return conductors).

Good luck.