Distance from substation and power lines 2

[buddy91082]

We have a porject in conceptual stages that is within 25 meters from a 27 kv substation and 130kv overhead distrubution corridor.

Any rules of thumb as to how far to remain away from the substation and overhead lines to mitigate EMI impact?

The facility in question is a biomedical research lab and hospital.

I assume relocating the overhead lines underground would help with an EMI influence on the facility.

Once the porject does get into production a full EMI study will be performed but we just want to get an idea of how close we can orient the building.

Thanks.
c

 

[EEIre]

Pretty good guidance can be found here:

http://www.esb.ie/esbnetworks/en/downloads/electric_magnetic_fields_in_environment.pdf

 

[jghrist]

Don't confuse EMF (electric and magnetic fields) with EMI (electromagnetic interference). EMI is a high frequency phenomenon that can be caused by corona around conductors, by loose hardware, or by bad insulators. It would be difficult to generalize about how far away you need to be to avoid EMI. EMI for smooth conductors can be calculated based on voltage, conductor diameter, and height. There is normally very little EMI around a power line with undamaged conductors and no faulty insulators. It would be best to measure the EMI at the site.

 

[buddy91082]

Isn't EMI the result of EMF?

 

[buddy91082]

Also, why do underground lines have a higher magnetic field than overhead lines but fall of more rapidly?

 

[jghrist]

Isn't EMI the result of EMF?

No.

Also, why do underground lines have a higher magnetic field than overhead lines but fall of more rapidly?

The magnetic field depends on the amount of current and the distance to the conductor. The magnetic field of three balanced phases cancel out if the distance is the same to each phase. The relative distance to each phase gets closer to being the same as you get further away. Phases are closer together on underground lines, so the field falls off quicker with distance.