Measurement Testing

Mjr · Site Admin Joined: 13 Jul 2005 Posts: 294

Some questions arose regarding the levels of EMI / RFI measured in 22kV indoor subsations -- specifically in 22kV/433V, 2000kVA transformers.

Two such transformers will be located in a switchroom within a hospital. There is a concern re: EMI/RFI to medical instruments, computers etc.
Is a distribution transformer a significant contributor of EMI?. If not what would be the worst offender. Do Standards specify maximum levels?. What are possible low cost-solutions (if any)?

Answers:

Switchgear in general and transformers in particular are large producers of EM fields. Interference with medical equipment and/or computers is, however, rare. Most modern switchgear rooms have electronic monitoring equipment which works without problems. This issue also depends on specific situations do you have.

Visit...
http://www.federalpacific.com/university/kfactor/kfactor.html
for: Common-mode noise
https://www.ch.cutler-hammer.com/docs/Fred/apscpgh/htmL/550000/l1.PDF
for: TVSS that incorporates the EMI filters