Radio Frequency interference

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Will B

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Fremont, CA
Hi all. We are having a problem related to radio frequencies being generated by a piece of equipment. Some background first:

The equipment is in a large manufacturing facility which uses Substations on the roof (12KV to 480V). The Substations then feed 480v buss duct in the ceiling. Out of the buss ducts are disconnects, then we run conduit to equipment, transformers, etc.

This particular case involves a piece of test equipment (really sensitive) fed from a 120/208V panel (fed from a transformer which is then fed by the buss duct). A new piece of equipment (480v) was installed approximately 1000 feet away powered by the same Substation. After the equipment was powered up and running, we started having problems with the test equipment. Fault codes showed that there were overvoltage spikes which caused the test equipment to shut down.

It took us a week to figure out that the new piece of equipment was the cause and the engineers told us that the equipment does emit RF.

Long story, but my question is, what would you do to protect the test equipment? Filter? Find an independent power source ( I am guessing that the RF is traveling on the conductors)? What do you guys/ gals recommend and why?

Thanks in advance!
 
Will B said:
Hi all. We are having a problem related to radio frequencies being generated by a piece of equipment. Some background first:

The equipment is in a large manufacturing facility which uses Substations on the roof (12KV to 480V). The Substations then feed 480v buss duct in the ceiling. Out of the buss ducts are disconnects, then we run conduit to equipment, transformers, etc.

This particular case involves a piece of test equipment (really sensitive) fed from a 120/208V panel (fed from a transformer which is then fed by the buss duct). A new piece of equipment (480v) was installed approximately 1000 feet away powered by the same Substation. After the equipment was powered up and running, we started having problems with the test equipment. Fault codes showed that there were overvoltage spikes which caused the test equipment to shut down.

It took us a week to figure out that the new piece of equipment was the cause and the engineers told us that the equipment does emit RF.

Long story, but my question is, what would you do to protect the test equipment? Filter? Find an independent power source ( I am guessing that the RF is traveling on the conductors)? What do you guys/ gals recommend and why?

Thanks in advance!
Click to expand...

First, positively identify the source of the interference.
Second, determine how the interference is affecting the equipment. Is the interference presenting on the power input, sensors, peripheral cabling, internal circuits, etc...
It coud be as simple as adequate grounding or so complex that it requires sufficient physical separation to stop disruprion of the sensitive test equipment.
 
eHunter said:
First, positively identify the source of the interference.
Second, determine how the interference is affecting the equipment. Is the interference presenting on the power input, sensors, peripheral cabling, internal circuits, etc...
It coud be as simple as adequate grounding or so complex that it requires sufficient physical separation to stop disruprion of the sensitive test equipment.
Click to expand...
+1
If the indications at the test equipment is overvoltage, and the 480 equipment is only emitting RF and not conducted line voltage spikes or large pulsed magnetic fields, then the problem may be accidentally non-linear (rectifying) connections which are transforming a pure RF pulse into a DC voltage proportional to the amplitude of the RF. If this is the case, both shielding and fixing the problem connections will help, but the latter is best! :)
 
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