Hi
There indeed can be significant issues around EM field strengths generated by 
the electrical supply system.
Refer to AS/NZS 3003, section 7 that specifies the limits.
These could well be something to put to the electrical design consultants who 
are proposing the location of the substation as design criteria to be met.
Adrian Richards
BME, WCH, Adelaide

________________________________
From: Geoghegan, Sean [mailto:sean.geoghe...@act.gov.au]
Sent: Friday, 30 September 2011 12:22
To: bmelist@bme.asn.au
Subject: [bmelist] Positioning of electrical substations near medical devices

Dear colleagues,

I have been asked whether there is any potential electromagnetic interference 
(EMI) issue with placing an electrical substation (with step down transformers) 
near a medical facility where the substation may be metres from x-ray equipment 
and potentially other medical devices. The substation is literally on the other 
side of a wall. It has been pointed out to me that it will all depend on the 
electrical loads and the resultant currents, the size of the transformers and 
the produced EMI.  I am told that most electronic and computer equipment 
utilise switch mode power supplies that inject 'hash' on the 240 V lines and 
produce significant phase shifts, but no-one is willing to state that the 
resultant EMI will not have an impact on the image quality of ultrasound and 
mammography units or other medical devices.

Do you have any experience with the placement of an electrical substation in 
relation to a medical facility and, if so, are there any concerns?

My initial impression is that if the substation is designed to Australian 
Standards (I am not familiar with them) and meet the EMR environmental 
requirements, then it is likely to be OK. If in doubt, then put in a Faraday 
cage.

Is this too cautious or justified?

Cheers,

Sean
Sean Geoghegan
Chief Medical Physicist   Medical Physics and Medical Technology Systems
Phone: 6244 2256 | Mobile: 0409 244 982 | Fax: 6244 3819 | Email: 
sean.geoghe...@act.gov.au<mailto:sean.geoghe...@act.gov.au>

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