EMC issues near National Grid sub-stations?

Discussion in 'EMC Matters' started by M0LEP, Apr 22, 2018.

  1. M0LEP

    M0LEP New Member

    I was visiting a house yesterday, and out in the garden I could hear something humming. The source of the hum turned out to be a fairly large electricity substation. I later found a footpath that went past the substation. It's in a fenced area about 50 metres by 10 metres, and has two three-wire high-voltage lines coming into it. Some of the distribution is by four-wire overhead line, but I think most of what leaves goes underground. The audio hum was something I could hear almost a hundred metres away. This left me wondering what other disturbance it might be causing.

    My web searches turned up some stories of RFI from substations, but they mostly seem to relate to situations where there's a fault at the substation, or when some fail-safe circuit-breaker kicks in. There's quite a bit about possible health effects, too, but the more rational ones end up pointing at the ICNIRP guidelines from 1998 and 2010 or related national recommendations.

    Given the volume of the sound from the substation, I'm wondering just how strong the electro-magnetic fields around it might be, and what effect they'd have on an amateur radio station within ear-shot of it. The only receiver I had with me was one of those relatively cheap Chinese 80 metres RDF receivers. I've used it for tracking down VDSL noise in the past. It didn't appear to point the finger at the substation in any clear manner. Of course, that's only part of one band, and far from conclusive...

    73, Rick M0LEP
  2. Ken G3SDW

    Ken G3SDW Moderator

    Rick, because you could hear an audible noise does not necessarily meant that it is radiating RFI,it may just be a mechanical problem.

    If the owner of the house is concerned about this then i suggest that they contact there local electrical distributor and judging by you location then it will be https://www.ukpowernetworks.co.uk/

    They will be able to assist it being put right.
  3. M0LEP

    M0LEP New Member

    Thanks. I was a little way from home yesterday, visiting Tetbury. The substation concerned is at about ST897934 ( https://goo.gl/maps/8nikFm561Pq ). Nobody else seemed to be bothered by the noise.
  4. Ken G3SDW

    Ken G3SDW Moderator

    In that case Rick it will be Western Power at http://www.westernpower.co.uk/

    Dont think anyone should put up with all the noise and i am sure if nothing else that Western Power would like to know for safety sake, better to be safe than wait for a bang lol
  5. M0LEP

    M0LEP New Member

    Thanks for the pointers. I'll pass them on.
  6. Ken G3SDW

    Ken G3SDW Moderator

    All part of the service
  7. 2e0wcg

    2e0wcg New Member

    I have an 11kV substation at the bottom of my garden. The transformer hums a lot, but the only EMC issue I have is that it wipes out all reception on top band. 80m and higher seem to be OK. I am in the middle of a town centre, so there is quite a high background noise issue anyway. My shack is about 4m from the transformer, which doesn’t help, but I get the same noise from an end fed wire with the low bit close to the substation and a mini G5RV with the apex about 25m away from it.
  8. Ken G3SDW

    Ken G3SDW Moderator

    Hi and thanks for contacting the Forum.
    You seem pretty sure it is the Transformer that is causing the problem.
    What have you done to prove that it Is?
    Before you do anything more you need to make sure that it is not coming from anywhere else and the first thing to do is to turn off your own mains supply at the main breaker and check with a portable rx to see if it is still there, that should be quite easy to do as it is only on 80/160m.
    Let me know how you get on
  9. 2e0wcg

    2e0wcg New Member

    Ken

    I’ve not turned my power off to the shack, but when I listened on 160m using my HT, the nearer I get to the transformer, the louder the noise received. I’ll turn the power to the shack off (it is 20m from the house) to eliminate that source, but there are other houses and shops closer than mine.

    I’ll wait for them to power down the transformer (made by Ferranti in 1962) and check then as well.

    Thanks for the feedback.

    Steve 2E0WCG
  10. Ken G3SDW

    Ken G3SDW Moderator

    No probs thats what i am here for.

    I am sure that there will be a large amount of noise from the sub station when you get close to it but before you point the finger you have to be sure.

    Power down your complete house not just your shack as that will not prove anything at all, we all generate lots of noise ourselves, never assume that we are all clean

    You say:- I’ll wait for them to power down the transformer (made by Ferranti in 1962) and check then as well.

    Do you mean that you have been in touch with, and i assume, Western Power.
  11. 2e0wcg

    2e0wcg New Member

    Powered down the shack - it made no difference. I'll try the house as well next week, but doubt it will prove much as there are 3 houses and 4 shops near the shack that are far closer to it than my own house.

    I haven't been in touch with western Power about EMC, but they are regular visitors to the substation as it is quite old and regularly needs attention, often in the middle of the night; the only access is through our garden.

    I'll see if I have a picture that shows how close I am to the substation.

    Thanks

    Steve 2e0wcg
  12. Ken G3SDW

    Ken G3SDW Moderator

    Never assume that it not yourself I hope it's not but often is, I deal with emc issues 24/7.

    I will leave it with you to sort it out and I am sure that if it us down to Western Power then they will be the first to rectify it.
  13. 2e0wcg

    2e0wcg New Member

    Thanks Ken

    It is just something I have to live with, being in the middle of a town centre, but thanks for your help.

    The transformer is the grey box you can just see to the left of the shed.

    Two of the shops behind the shed sell mobile phones and the other two are a Costa and a butchers. Just out of shot to the left are 4 houses, one of which has solar panels.

    Steve



    [​IMG]
  14. Ken G3SDW

    Ken G3SDW Moderator

    OK Steve must agree it's rather close and do those type of shops must use lots of SMPS especially the mobile phone shop.

    Solar PV installations will only give any problems in sunlight.

    Let me know how you get on.
  15. 2e0wcg

    2e0wcg New Member

    Ken

    I have made some progress.

    1) Powered down the main house - no difference.
    2) Took a video showing the noise, and why I thought it was coming from the transformer :

    It is not great, but you should be able to hear that the noise I get on top band SSB is the same as you hear when the HT antenna is next to the transformer. The time it takes me to get from the shack to the transformer shows it is close. Yes, I realise that the danger of death notice is there for a reason.

    HOWEVER...

    While I was uploading the video, the noise vanished. I couldn't hear anything on the HT either. This was around 16:50. While I was typing this, it came back (17:35)…

    So, my theory is now that the noise is being transmitted by the transformer, but originates somewhere else - either elsewhere on the network, or backfed from something in a building connected to it.

    It looks like I will need to keep a log to see if there is any pattern to it.
  16. Ken G3SDW

    Ken G3SDW Moderator

    Well if it has done what you have said then i think we can rule out anything there being faulty.

    What it s most likely to be is a close neighbour and judging from the sound then it is very similar to TV time base but with today`s TV`s then that is unlikely.

    On face value it sounds like a Plasma TV.

    Your demonstration of you going close to the transformer is confusing the situation, as it only acts as an antenna, making the sound much stronger, i get this in most cases i deal with every day, one thing i noted is that whilst close to it the noise varied quite a bit, if it was coming from there, and you being that close to it, then the noise would be constant even though you moved around a bit.

    Talk to your neighbours to see if they have a Plasma TV and maybe if they are willing too, get them to power down there house for you and check again as it being that strong then it is very close to home.

    I know that knocking on doors is not what we want to do but sadly in many cases it has to be done.

    Keep in touch.
  17. 2e0wcg

    2e0wcg New Member

    Thanks Ken

    I’ll have a look to see if I can pick up the noise on the HT. I only hear it when I point the HT antenna directly towards the transformer. It did seem odd, which is why I thought that I’d video it. I’ll have a wander round with the FT817ND to see if I can identify where else it is picked up. I’ll try keeping a log of the noise to see if I can pin it down before I go knocking. If it is a business it should keep office hours.

    That approach helped me track down some VHF interference which was caused by some LED lights in a nearby restaurant. They changed the really bad ones (demonstrated using an FM radio) when I explained that was probably why their card machine wasn’t working away from the base unit!

    Any suggestion on a suitable portable antenna for picking up Top band interference?

    Thanks

    Steve
  18. Ken G3SDW

    Ken G3SDW Moderator

    As it is 160m then some sort of ferrite rod antenna would be ok.
    By going close to anything like for instance phone lines etc will increase the noise.
    When you get max noise then take off the antenna and if you are on it then there will be very little change in the noise level
  19. 2e0wcg

    2e0wcg New Member

    Ken

    I used the rubber ducky on my FT817ND as it was picking up the noise. It reduced as I went away from the station, but picked up as I went into the house. The noisiest bit seemed to be the router but the interference was still there when it was disconnected.

    I then followed the phone lines (round here they are fastened to walls about 6’ above the ground) going towards the distribution box. The noise got louder but faded as I approached the box (about 30m from my house). Backtracking, the noise was loudest outside a shoe repairers so I went inside, the noise getting louder.

    The owner turned the machine off, but although the level dropped, the noise was still there. However it vanished completely when he turned to 240 to 415v inverter off. It looks like this unit has optional rfi filters from the online manual I found.

    My next task is to check there isn’t any other source of noise when the shop is closed.

    Steve
  20. Ken G3SDW

    Ken G3SDW Moderator

    It's very rare that there is only one source of noise but it seems a s though you found the main culprit.
    So concentrate that one first as that is giving the biggest problem.
    As for the rest well you can decide on whether or not to peruse them or not.
    Nice to get a positive conclusion.

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