High Voltage Substation

I agree

by Good Dog - 2016-12-11 08:36:48

I have had similar experiences. I once put my hand on and leaned against one of the turbines at the U.S. Niagara power station dam. I worked a large part of my life on and around switchgear, generators, VFD's and both syncronous and induction motors up to 11,000 volts and 3,500 h.p. 

I have also used chain saws and other equipment that is contained in the warnings. All of this mostly out of necessity, but my attitude has been to approach it cautiously and if I feel O.K., then not to worry. I have never had a problem. 

These devices (mine a Medtronic) are rugged and shielded very well.

David

I agree too

by Edward GT - 2016-12-11 09:20:18

Yes, I agree with you GoodDog. Thanks for your reply.

My experience with being close to machines includes Threephase Power Transformers, like 78 MVA 225kV to 72 kV, and as I noticed, I can be as close as standing by its side without any problems. I used a magnetic detector to measure magnetic fields arround, and it seems that the magnectic field keeps confined inside the enclosure.

Of course, as you said, it is always necessary caution. These are limited experiences, and no "general rule". But that is the objective of my post, to gather information from other pacemaker / ICD users to build a network of information. Through sharing information, it is possible to virtually increase each one's experience when deciding what places can be considered to be safe or not.

One important aspect, is that the device has to be bipolar (most of modern devices are bipolar) for higher immunity.

Couple of data points...

by donr - 2016-12-11 09:29:00

...on getting close.  1)  we have buried electric service at our house w/ a green surface placed transformer.  Don't recall the input voltage, but it is POCO line voltage in their dist system.  Several times I have used that box as a work table for doing something in the front yard.  On several occasions, I droppped a tool thatwound up on the gfround on the far side of the box.  I leaned over the box - actualy laid my chest n the box - to pick up the too.  No adverse effect on my PM. 

2)  About two weeks after getting my PM in Feb 2003 I was climbing up into the rafters in my shop Bldg.  The electric water heater supply line ran right past the spot where I climbed.  My PM passed about 6 inches or less from the cable.  Apparently the heater was on at that time & I felt the pM go into its test mode.  Surprised me so much that I nearly fell off the ladder in my rush to get down.

Donr

Well EE's

by Grateful Heart - 2016-12-11 12:36:00

Can you talk some more about unipolar leads.

One of my leads is unipolar due to a lead revision/ splicing.  I have posted here before that I believe this is why I feel my device go into test mode if near a magnetometer or set off security alarms in some stores.

Your expertise please?

Grateful Heart

Well EE's

by Edward GT - 2016-12-11 12:43:05

Hello Grateful Heart.

From what I have studied up to now, in litterature, it is well known that unipolar leads are more sensitive than bipolar leads. Anyway, it seems that for common daily situations there should be no problem, unless you work wih some activity that has electric or magnetic fields. Do you ? If you do, we can further discuss your particular situation. In the other case, just live your life and don't worry. Your physician would have warned you if there were any risks, which I think there isn't.

Best wishes.

Not worried

by Grateful Heart - 2016-12-11 13:25:22

But it has been the topic here more than a few times.  A few naysayers who don't think it is possible to have interference with store security systems or magnetometers, while a few of us have indeed experienced it more than once.  I have read that unipolar leads are sensitive too.

No, I don't work in the field. I've had my CRT-D for 8 years and I am always interested in learning more about this wonderful device and from what I have read, my unipolar lead is likely the cause for the sometime interference.  Just thought you could shed more light on it....thanks for your time.

Grateful Heart

Increased sensitivity with unipolar leads

by Good Dog - 2016-12-11 16:27:08

I never really thought about it until you mentioned it. Here is my understanding:

Unilike with a bipolar lead, a unipolar lead does not return the signal to the pulse generator via a metalic conductor. It sends one, but it is not returned through the lead. Instead, the unipolar lead returns the pulse to the generator via tissue and body fluids. So since the pulse is not conducted directly to the generator via a metal wire (bipolar lead), it makes sense that your generator is much more sensitive than a PM with bipolar leads. It needs to be to operate properly. From what I have read, there is no doubt.

"Unipolar leads are much more sensitve and suseptable to oversensing than bipolar leads." So it simply makes sense that a mild electrical/magnetic field could cause it to operate.

That would seem to answer the question why only some devices are impacted. I'd only be guessing with regard to why it would set-off a security system. 

Thanks GoodDog

by Grateful Heart - 2016-12-11 19:04:15

There isn't much on the internet.  Every now and then I will do a search to see what else may come up about unipolar leads and sensitivity.  This is the latest I have found.

 https://www.ncbi.nlm.nih.gov/pubmed/21084360

I find this all so facinating!

Grateful Heart

Interesting.....

by Good Dog - 2016-12-11 20:11:51

THANKS! That IS interesting stuff! That article basically indicated that doctors were implanting many (14) of those unipolar pulse generators without even programming them.  They also discovered that the sensitivity settings for left side implants were not optimally adjusted to avoid interference. Many were set at less than 2 millivolts. They said they needed to be 3 Mv or higher. Their findings also indicated the need for more education for doctors. Thank goodness that is not in the U.S. although I guess it may be a problem here.  However, after reading that abstract it seems that your sensitivity may be set too low? I mean, what do I know, but that was the supposition when patients were subject to EMI (electromagnetic interference).

From what I've read; the benefits of unipolar leads are the small diameter and the fact that they can be repaired easily. I don't know much about any of this stuff, but I am trying to learn. It seems that a mild electromagnetic field can screw-up the whole works with a device using unipolar leads.

Unipolar EM fields

by donr - 2016-12-12 04:02:51

GH:  Here's the gospel according to a guy named Shelkunov, who wrote the first book I ever suffered through on EM fields way back in 1962.

On a Bi-polar lead, the pulse travels outward on a wire, gets deposited in the heart muscle & almost immediately is picked up by another wire conductor to be returned to the PM.  The tissue/blood gap between the two conductors is very small - probably on the order of a couple millimeters (For the inch people among us, a millimeter is 1/25th of an inch, so pretty small.)  The interfering external electrical field cannot affect the current inside the wires - it's too weak to do so.

The Mono-Polar lead, OTOH, has a blood/tissue gap of several inches between the end of the lead depositing the pulse & the point where it is picked up by the exterior of the PM case.  Now the PM case is about 2 inches in diameter & the terminal end of the outward conductor is about 1/10 th of a mm in diameter.  Mentally draw a bunch of lines from the Point of the lead going to the heart to the 2 inch diameter case.  For simplicity sake, imagine  25 lines all starting at the point but distributed evenly across the surface of the case. Obviously, they will be separated quite a bit when they get to the case.  Now all the little electrons flowing back to the case distribute themselves pretty evenly along those lines.  Pretty thinly distributed when they get there, as opposed to when they leave the point at the heart.  (Electroms are just like two women showing up ata party wearing the same expensive dress - they avoid one another like the plague!)  Apply some external EMI to the situation & compared to the strength of the field causing the electrons to return to the PM it can easily be less than the external field - just like you meet in a store security device.  Especially if it is a magnetic device.  You mentioned magnetometers - YEP - that'll do it.

Now you have about a 4" gap for the external field to influence.  That can play hob w/ the return current & the inner workings of the PM system as a total.  That's why you might feel like you stepped in something that Rover left in the back yard.

My apologies to good old Schelkunov - I felt him rolling over in his grave from the simplification I made to field theory 101, which is pretty darned complicated at its simplest.

Enjoy!

PS, BTW:  The only MD I know who knows beans about this subject is our MD Daughter, who has a BSEE & took her course in EM fields from the same Schelkunov book I used some 20 yrs earlier.  Fortunately it had been edited several times to clean up some errors in  it.

Don

EMI Interference

by Good Dog - 2016-12-12 08:54:46

Donr, that was very interesting and informing. Thank you.

Here is an excellent source to help understand not only unipolar, but lots more:

http://clinicalgate.com/engineering-and-construction-of-pacemaker-and-icd-leads/

Grateful heart: 

Also, as I indicated in the previous post, the information in that  abstract was quite alarming. Another something I learned is that unipolar leads are much more reliable than bipolar. Probably the most relevent fact that I gleaned from it really is the importance of the sensitivity setting. Obviously its already been established that with your device EMI can be a problem. Their research revealed a surprising number of devices in which the sensitivity setting was too low (below 3Mv), which obviously made them more suseptable. So that is something you can ask your doc. It may be helpful and it doesn't hurt to ask. 

David

Thanks EEs

by Grateful Heart - 2016-12-12 23:02:50

Thanks for the info EEs!   That explains a lot.  I knew if I persisted, over time I would get some answers.  :)

The sensitivity settings for my device are much, much lower than 3mV.  I do not see my original EP on a regular basis, just once in a while if there is a problem, however, he is not the EP who did the lead revision, placing actually part of the lead as unipolar.  (To be continued on that one).   

Don:  I thought you were hibernating with your bears.  Great explanation, thank you....and thank your MD daughter for me too.

David:  I haven't had a chance to look at the link but I certainly will.  Since I have realized the interference I sometimes encounter, I just walk briskly through when I am aware of it. 

Grateful Heart  

That Link

by Good Dog - 2016-12-13 07:57:15

You are welcome. That link (the one you provided) really raised a startling awareness for me (maybe just ignorance on my part). I can only speak for myself, but it was unsettling to see the number of people with lives that were likely negatively impacted by doctors that either didn't know or didn't care. If they didn't know any better, that doesn't seem like a legitimate excuse. In either case, there seems to be large numbers of folks mistreated.

Makes me want to learn and understand much more about my device.

Sincerely,

David

Working in an industrial area

by aintgotnohair - 2020-12-29 01:19:47

I am an IBEW Journeyman Inside Wireman who received a PM a year ago. When I went back to work a few months later, I was worried how my PM would affect the jobs I could do. The refinery and chemical plants that I normally work in have many potential problems such as high voltage substations, motor control units, cogeneration untis (big enough to power a city), transformers mounted near A/C power panels, various welders used for construction, etc. With the information I've found on this forum I've been able to successfully return to work.

First off, I'm up front with the people I work with and I let them know I may have to work around problems I might encounter due to magnets. Like, if I have to use a magnet drill, I just don't. I get my tool buddy to drill the hole or use a portable drill. One day, I needed to work right next to a large trailer welder. I let my foreman know I couldn't work right next to a running welder. He was able to reschedule my work the next day when the welding was over.

Second, I don't hug things. I don't hug pump motors, large industrial compressors, drills, bandsaws, running transformers, running generators (the portable ones or the massive cogenerator turbines). I just don't do it. It hasn't affected the work I do. 

Third, if I go into a motor control center I always stay a couple of feet away from the cabinets. Doing this insures my safety and the safety of the things they are running.

So, all it takes is to slow down your thinking before you do a job. Fast thinking can get you hurt. Think about all the things a particular task that could get you hurt, including setting off your PM. Then, figure out how to do it safe. The people you work for and the owners of the facility you work at should have your safety in mind. But, when it comes down to it, YOU are in charge of you being safe.