Radio Noise on power lines

[McQueen]

Hello folks, and welcome to my first post

My company would like to buy some RF detection equipment to detect the location of sources of radio noise from our power lines. The most common source of this noise seems to be faulty lightning arrestors. I've found a wonderful little meter that is about 1/10th the cost of the average spectrum analyzer, but its limitation is that it can't read anything below 100 kHz. I'm wondering whether this is a problem or not. Does anyone out there have any ideas on some typical frequencies that I might find on the lines that might cause RF interferance?

 

[SphincterBoy]

Additional sources of RF noise are 1.) MV photoeyes, and
2.) "touch" switched lamps.

 

[tgott]

Some notes I took from an RFI seminar:
Power Line Radio Frequency Interference; Noise = Power Line RFI, can be visual(e.g. TV) or audible (e.g. radio)
so Noise = RFI which consists of TVI and RI
Sparking - arcing between 2 parallel conductors. Different charges on conductors that try to equalize; loose connection with small gap, less than 1 mm. Sparking causes broadband interference, not just one specific frequency (AM range all the way to cellular phone).
Corona - partial discharge into air; usually atmospheric conditions have to be just right. Can be seen at night. Corona has no energy behind it whereas sparking has the power line energy behind it. Problems with corona will usually occur in the AM frequency range and will be very close to the people who are having RFI.
59.96 Hz - TV picture synch frequency
60 Hz - AC power frequency (of course)
6000 Hz - audio range
40,000 Hz - ultrasonic

535 - 1605 kHz - AM radio
1.8 - 10 MHz - shortwave & Ham
54 - 88 MHz - TV ch. 2-6
88 - 110 MHz - FM radio
(I didn't get the frequencies for TV ch. 7-13, and ch. 14-88).
Low frequencies are detectable farther from the source than high frequencies. Low frequency interference can be detectable up to 12 miles from the source. Low frequecy and high frequency interference is caused by some gap. Causes:
loose mounting bracket, pole top unit
loose staple near top of pole
guy touching or very near neutral
loose bracket bolt, clamp bolt, pivot bolt
loose clamp, hot line clamp, splice
trash on the line
pole ground wire under guy wire plate
cracks in insulator
slack suspension insultators, do not have uniform pressure and an arc is between the ball and socket
Investigate only when noise is "ON". Fair weather or breeze RFI may point to water in a gap and then when it drys out, sparks can occur. Do not go check in rain or foul weather, nor early in the morning because of dew.
About 50% of RFI complaints are generated from the residence itself. Common problem is the doorbell transformer. Other problems:
heater thermostat puts noise on line that is conducted to a neighbor who gets the RFI
fish tank thermostat
electric blanket thermostat
fans
light dimmer controls
switch contacts, found in dishwashers, refrigerators and other home appliances
aquararium or waterbed heater
furnace controls
home computers
fluorescent light ballasts
neon lights

 

[SphincterBoy]

We use RFI/TVI locators made by:

Micro Tech Mfg., Inc.
100 Grand St.
Worcester, MA 01610
voice508)752-5212
fax508)754-2415

email: interferencelocators@microtechmfginc.com

website:

http://www.Microtechmfginc.net

I hope this will help!

 

[busbar]

One "homespun" approach is:

http://www.qsl.net/n8dmt/powerline.html

with the comment:
'I find it to be pretty amazing that the FCC considers RFI to licensed radio services to be outside of their domain...'
And:

http://www.sadona.com/news/news3.html

 

[Bung]

An ordinary medium wave AM receiver (any old cheap one will do) tuned off station is prety good as a rough and ready instrument - just listen for the fizzing and popping. By moving it around you can use the directional characteristic of the ferrite aerial to track down roughly where the problem is. This works pretty well where the RFI is severe enough to be interfering with somebody else's radio.
Bung

 

[ccaserta]

For conducted noise the normal frequencies to be concerned with are 150 Khz to 30 Mhz for conducted emission noises. From 30 Mhz to 1 Ghz are radiated noises that will interfere with your equipment. These are the frequencies that your product would be tested to if you submitted it for European/and FCC approval.
Your money may be better spent having a test lab come in for a day with their very good equipment and map out your faciltiy for you. Once this is done use your device to make the same measurements. Now you have a reference to a known number versus the equipment you have in house. This may be worth performing on yearly bassis as the environment around you changes. Christopher Caserta
ccaserta@enorthhampton.com
Ph:904-225-0360