I own a 32 unit park in Canada. It’s about 40 years old.The power company owns the power right up to the park boundary. I own all the secondary power lines in the park. The power company individually meters each home and is responsible for collecting from each home - I have no liability for collecting on the power companies behalf. I am responsible for the secondary line infrastructure. I am not sure if this means its master metered electrical or not. Twice in the past 6 months the transformer feeding the park has blown. Likely the transformer is undersized. While we have added about 10 % load to this transformer over the past 6 months, it has otherwise worked well. Having said that my electrician says the current transformer seems very undersized given the expected load (but again, it has worked well for many years). If it’s just the transformer, upgrading is manageable.My concern is that the parks lines are slowly breaking down over time and current throughout these lines are leaking into the ground, which increases the power demand even more. In this case, potentially the lines within the park will need to be upgraded. Has anyone every seen this? How likely is it that this is the case? If this is likely, any suggestions for best next steps?Thanks,
There is not nearly enough info to give a really good answer as to what your problem is.Your question about electricity “leaking” into the ground is not terribly off base, but really isn’t likely. “Leakage” isn’t impossible, but not likely. Electricity isn’t like a leaking plumbing pipe. Did the transformers blow after a heavy rain? Is the transformer fused?Your electrician should be able to roughly calculate the load on the transformer, it’s actually fairly easy to even monitor the load on it.There are many, many factors that need to be taken into account. Were the services originally 60 amp then later upgraded to 100-200 amps? Was the park built before AC was common?I’m infrared certified, but not in this particular area. If you find someone that has the proper infrared certification they can check the temperature of the transformer under heavy loads also.My advice would be to contact some large, major electrical contractor companies. Ask if they have engineers on staff, or someone that can handle this for you.Having an electrician say it “seems undersized” is troublesome. You need someone more qualified to tell you what size transformer you need. Also, depending on the design of the system, the wires leading to, and away from the transformer may also need upgraded if you put in a larger transformer. It just depends on how the system was originally designed. Did the original designers plan for future demand when they chose the wire size?This really isn’t rocket science, the right person can tell you exactly what you need after crunching a few numbers.
You need a load study. First, a set of instantaneous readings will give you a snapshot. Your electrician is perfectly capable of doing this. The instantaneous readings are compared to the transformer nameplate kVA rating and they must be less. After this, a 3 day to 7 day recorded study should be done. You might have to call around to find someone who can do this. But your utility should do this to make sure that they are serving you well. The addition of 10% load should not have made a difference since there should be at least that much reserve capacity in a utility transformer.As for ‘leakage’ current, it doesn’t work that way. Once electricity leaks to ground or to another conductor it becomes a catastrophic failure. That is, a short circuit. So, there are 2 kinds of short circuits, line to ground and line to line. Either one should be cleared, or stopped, by the circuit protective devices on your distribution system, these devices are fuses or circuit breakers, before the transformer overheats and blows out. If anyone is interested, I’ll post the formulas for converting amperes to kVA, or you can by the Ugly’s Electrical Reference book, about $10 at reputable hardware stores and electrical supply houses. If your utility is BC Hydro they are pretty doggone good as I recall. Jim Allen
Wow, Jim Allen and Coach62 you are very knowledgeable! Thank you for sharing your wisdom!Even though I did not post this question nor do our MHPs have this issue, it is always great to learn from others. Thanks So Very Much!
Yes, thank you very much. I appreciate your insight and will use this info going forward.
cbredo what province are you in. I have a park same size and age as yours in Ontario. As said by others leakage is not your problem. In fact you do not have a problem your utility company has the problem. It is possible the second transformer was somehow defective or was effected by other outside factors. If it happens again you should be having a discussion with the utility company about fixing their problem but the likely hood is that if it does happen again they will also be just as interested in solving their problem.For now I would do nothing and wait to see.
Greg makes a good point about your utility company. A possible scenario is where the first xfrmr blew out due to age. The second xfrmr blew out due to being defective, the so-called infant mortality curve. In reliability engineering, it is called the bathtub curve and there is a short article on Wikipedia about it. In the hospital industry we use the term bathtub curve. Nevertheless, the best things to do for right now are nothing and wait and see.A note about circuit protective devices, as I know from experience that they aren’t well understood and many people don’t see a problem putting in a bigger fuse or CB when there is a repeated tripping or blowing problem. That is, just because a CB is tripping or a fuse is blowing solving the problem isn’t done by putting in something with a bigger rating. CBs and fuses are rated and coordinated such that the device nearest the fault is supposed to clear the fault without the upstream feeder equipment incurring any damage. This is coordination in its simplest form. So, in ten words or less, don’t re-rate circuit protective devices to higher values. To be clear, I’m not implying that anyone is doing this with their MHP, but the subject does come up in my world. Just a word to help folks on this forum stay out of trouble.Jim Allen
I probably should have mentioned earlier, I have a degree in electrical engineering.To be clear, F&T’s post is very good, but it is actually possible to have “leakage” without having a short. That’s why I asked about recent rains.I could write a page on the subject, but Fluke (perhaps the largest electrical instrument manufacturer) has already done that. Here is a linkhttp://www.fluke.com/fluke/uses/comunidad/fluke-news-plus/articlecategories/electrical/leakagebasics.htm