Stray currents from overhead power lines?

[Craig Thomson]

Just back from blacking our boat for the first time (40ft live-aboard, 2002 build) and slightly paranoid about electrical corrosion after seeing first hand the amount of pitting on her sides and bottom.

 

There is widespread pitting of 3 or more mm across the baseplate. We cleaned and blacked it all (well except for where she was resting on the bearers), but are now looking to what we can do to prevent further corrosion worsening the state of the hull.

 

We intend to get an isolating transformer to deal with any stray current from the shore line (we are permanently attached at our home mooring) but then I also got to thinking and realised that our mooring is directly beneath overhead power lines (see picture below ...)

 

So what I want to ask is - is it possible/likely that stray current from high voltage power lines could cause electrolytic corrosion to a steel boat hull? If so, how would one measure such a stray voltage and what could be done to insulate the boat from it? (Aside from moving to another mooring, which we are likely going to do anyway as a precautionary measure!)

 

Any insight from the electrically minded much appreciated.

 

CT

 

 

[Alan de Enfield]

It many also worth condisering invetigating to see if it is MIC (which is nowt to do with electrical corrosion) but is becoming more common.

 

There are more ways a boat can corrode / errode rather than just leaky electrics.

 

Edit : linky not working - try again :

 

 

 

 

 

 

MICROBIOLOGICAL-CORROSION.pdf

Edited July 12, 2021 by Alan de Enfield

[Tracy D'arth]

I don't think it has ever been proven but there must be a possibility of current as I know of one guy in a bungalow who had managed to get his fluorescent tube lights to strike up because he was under a 400kV line. He never turned them off!  He was eventually prosecuted by the power company for the theft of electricity. 

[tree monkey]

I don't know how likely it is but I do know when doing the training for working on or near EHV or national grid it was recommended to earth any vehicles sat under the OHL.

I don't know anyone who actually did this but it was part of the training. 

 

I also remember getting static belts/shocks when climbing in fog next to National Grid towers /lines, which was always a little unpleasant 

 

only national grid stuff though, I can't make out what type of tower you have there.

 

how this effects galv corrosion I have no idea, sorry

Edited July 12, 2021 by tree monkey

[GUMPY]

There was an article in Wireless World many years ago about how living under power lines causes all sorts of cancers and how other countries have a 150meter exclusion zone along the line of the pylons but we dont.

 

[blackrose]

I don't know about other stray currents, but galvanic corrosion occurs between two dissimilar metals immersed in an electrolyte (water). There has to be a circuit through the electrolyte for this to happen. If your galvanic isolator or isolation transformer is protecting the boat then surely it would still protect the boat if the hull is inductively charged through the air by the power lines above - until the limit of the isolator is reached of course, but then you would see that on the status monitor (assuming the isolator had one).

 

I have to caveat these points by stating that I have no electrical knowledge whatsoever. 

5 minutes ago, Loddon said:

There was an article in Wireless World many years ago about how living under power lines causes all sorts of cancers and how other countries have a 150meter exclusion zone along the line of the pylons but we dont.

 

 

Sounds like the OP is rather f@cked then, never mind about the health of his hull!

[GUMPY]

7 minutes ago, blackrose said:

Sounds like the OP is rather f@cked then, never mind about the health of his hull!

Lots of reading Here re the health risks especially childhoid lukemia

 

[Arthur Marshall]

2002 build, just doing its first blacking. Presumably the OP has only had it a couple of years, but they won't know how often it's been done in the past. Mine needed replating after twenty years and again twenty years later, so it sounds pretty normal to me.

[Grahamnewman]

Move your boat away from the pylon asap. Read up on stray current from these metal structures. 

fishermen with carbon fibre fishing rods feel huge vibration when trying to fish beneath these power lines.

Not the best place to moor under any circumstances.

[Tracy D'arth]

2 minutes ago, Grahamnewman said:

Move your boat away from the pylon asap. Read up on stray current from these metal structures. 

fishermen with carbon fibre fishing rods feel huge vibration when trying to fish beneath these power lines.

Not the best place to moor under any circumstances.

If the fishermen maggot drowners feel "vibrations"  ( interesting word ) what about the fish? Are there any there?

Are the C&RT signs which we pay for placed for this reason and not just for the safety of the miseries sat on the bank?

[Ray T]

I know it is for metal pipes but have a read of these:

 

36055659.pdf (iaea.org)

 

(1) Is living under high voltage power lines bad for our health – Emf Protection Store

 

I worked for BT in my career and in old long distance copper cables capacitance, induction and resistance was always an item needing addressing.

 

I also had to be aware of the effects of HV power lines.

 

 

Edited July 12, 2021 by Ray T

[Grahamnewman]

6 minutes ago, Tracy D'arth said:

If the fishermen maggot drowners feel "vibrations"  ( interesting word ) what about the fish? Are there any there?

Are the C&RT signs which we pay for placed for this reason and not just for the safety of the miseries sat on the bank?

Me thinks CRT dont want to kill off the other canal users. No such warning for us boaters !

[tree monkey]

1 minute ago, Grahamnewman said:

Me thinks CRT dont want to kill off the other canal users. No such warning for us boaters !

I think you're being a tad excessive with your warnings, it's perfectly sensible not to use a conductive 15m carbon fibre pole under a OHL of any type more because of the danger of lifting it and contacting the conductor or entering into what is considered the "live zone", that would be a bad thing

 

I suppose there could be a chance of inductive current in the pole as well but I've never heard of it happening, not to say it couldn't. 

 

There does seem to be some concern about the presence of OHL running over where you spend a long time but that's a long term exposure issue and certainly not a problem in the short term and quite frankly almost every property in the UK is in close proximity to OHL or underground conductors from 240v to 400KV.

 

It's certainly not something to panic someone about, make an informed decision yes but not panic about

[frangar]

My mother worked in the burns unit in Essex…they got quite a number of fishermen that had tested out how well fishing line and carbon rods conduct HV power….quite often it jumped rather than direct contact…a good way of sorting the gene pool. 

[AndrewIC]

There are some bits of the Macc where HV power lines run across the canal at a very shallow angle, so you are passing under and almost parallel to them for some distance. Trundling along there one particularly hot and dry summer day, wearing a short sleeved shirt and with my bare forearm resting along the brass tiller tube, there was enough induced voltage to cause a tingle.

[Sir Nibble]

I don't know. I am struggling to see how the 3 phases superimposed upon one another would work as a transformer primary. If there was a lot of induction at work then each phase should be interfering with each other as well as dumping to earth. I suspect any observable effect is capacitive in origin. But like I said,  I don't know,  but I would like to.  The flint axe technician within me says that if frost forms on the pylon in winter, there's no problem. 

[Craig Thomson]

1 hour ago, Arthur Marshall said:

2002 build, just doing its first blacking. Presumably the OP has only had it a couple of years, but they won't know how often it's been done in the past. Mine needed replating after twenty years and again twenty years later, so it sounds pretty normal to me.

 

The boat is indeed new to us, we've been living aboard since April last year. Just slowly getting to grips with all the various aspects of maintenance.

 

 

The amount of pitting on the hull, though noted in the previous boat report from 2019, was a bit shocking to see first hand. From what I gather some boats just seem to rust like hell and others somehow manage to get on fine for a hundred years and nobody quite knows why. Environmental factors surely have something to do with it, as do things like mill scale being left on new boats etc. Bad and extensive pitting though, seems to me to be likely down to electrical issues somewhere, about which we currently have little expertise.

 

The boat is fitted with a galvanic isolator, but no idea whether it is in serviceable nick or not. Anodes are wearing ok and providing some localised protection to the bow and stern but not seemingly anywhere much else.

 

As for the power lines, it is my gut feeling is that they must certainly be inducing some kind of voltage/current in the hull of the boat, but whether or not it is enough to do substantial damage is a bit of a mystery.

 

We were considering moving the boat soon anyway to be closer to my other half's workplace so it shouldn't be a big problem for us to relocate.

 

It seems to be a difficult situation to find any solid information on as it is so specific to canal boating (I can't imagine a lot of seagoing vessels are likely to encounter such an eventuality!)

 

 

[Grahamnewman]

33 minutes ago, tree monkey said:

I think you're being a tad excessive with your warnings, it's perfectly sensible not to use a conductive 15m carbon fibre pole under a OHL of any type more because of the danger of lifting it and contacting the conductor or entering into what is considered the "live zone", that would be a bad thing

 

I suppose there could be a chance of inductive current in the pole as well but I've never heard of it happening, not to say it couldn't. 

 

There does seem to be some concern about the presence of OHL running over where you spend a long time but that's a long term exposure issue and certainly not a problem in the short term and quite frankly almost every property in the UK is in close proximity to OHL or underground conductors from 240v to 400KV.

 

It's certainly not something to panic someone about, make an informed decision yes but not panic about

I speak from experience.having moored under one of these power lines on the Leicester line just outside Yelvertoft my TV, battery monitor and inverter all had strange 'occurrences ' which returned to 'normal' once i moved away. I have read various documents advising not to stand underneath or spend too much time beneath these power lines.

[tree monkey]

Just now, Grahamnewman said:

I speak from experience.having moored under one of these power lines on the Leicester line just outside Yelvertoft my TV, battery monitor and inverter all had strange 'occurrences ' which returned to 'normal' once i moved away. I have read various documents advising not to stand underneath or spend too much time beneath these power lines.

Not denying your experience but I spend 20yrs working next to the whole voltage range climbing trees next to live conductors and spent 2yrs working directly with engineers, linesmen and tree teams organising live and shutdown pruning.

Different experiences different opinions.

 

 

[tree monkey]

22 minutes ago, Sir Nibble said:

I don't know. I am struggling to see how the 3 phases superimposed upon one another would work as a transformer primary. If there was a lot of induction at work then each phase should be interfering with each other as well as dumping to earth. I suspect any observable effect is capacitive in origin. But like I said,  I don't know,  but I would like to.  The flint axe technician within me says that if frost forms on the pylon in winter, there's no problem. 

I do know we were told to earth vehicles when working under Nat Grid and static shocks were if not common were not all that unusual in the right weather conditions, 

Actually another issue was  during a shutdown earthing an OHL near an underground section due to "magnetic resonance " I think was the term, in effect it could cause the earth to go bang when trying to connect up to prove the line was isolated.

My understanding was practical rather than technical tbh, so I don't know what, just it was bad thing

[JRT]

There is little or no evidence of electromagnetic fields having any long term health effects 

 

.....the overall evidence for adverse effects of EMFs on health at levels of exposure normally experienced by the general public is weak. The least weak evidence is for the exposure of children to power frequency magnetic fields and childhood leukaemia. 

 

see Electric and magnetic fields: health effects of exposure - GOV.UK (www.gov.uk)

[Jim Riley]

Wrap boat in tinfoil, make hat with leftover bits. Job sorted.

[GUMPY]

1 hour ago, JRT said:

There is little or no evidence of electromagnetic fields having any long term health effects 

 

.....the overall evidence for adverse effects of EMFs on health at levels of exposure normally experienced by the general public is weak. The least weak evidence is for the exposure of children to power frequency magnetic fields and childhood leukaemia. 

 

see Electric and magnetic fields: health effects of exposure - GOV.UK (www.gov.uk)

Well they would say that wouldn't they.

 

[tree monkey]

11 minutes ago, Loddon said:

Well they would say that wouldn't they.

 

There was a story going around that Nat Grid wanted to move their head office off site away from under some serious EHV lines, in effect a hub where part of the network radiated from, not for health and safety reasons of course, but it was decided it would be seriously bad PR so had to stay

[David Mack]

If this is permitted, surely a boat should be OK.