Electrical Engineering

A short?

I think that's a safe assumption!

You might try "Aggreko generator rentals".

What kind of short circuit protection was present/absent on the other transformers?

They rented a transformer and I was mistaken, primary is 4160. As far as protection, I'll know Monday but as you, if proper protective relaying was installed this should have never happened. I suspect downstream problems but I would guess that the secondary circuit breakers are reverse feed type so it could have tripped ahead of the breakers. Not enough facts at this point, ship is in Panama but will be in Texas soon.

Thanks,

Thanks for the help. We went to them and rented a 2500 kva xform but check this out; they want $17k/mo for cable rental. We're in the wrong business. Don't buy gold, buy copper!

Thanks again,

Jim

The two transformer tripping one after another is not a particularly appetising phenomenon.

What are the ages of the transformer? Find out any history of repairs or any other background.

The first one is an insulation failure. Assuming the second one is too, the first suspect is the atmosphere. There has to be some aggressive ambient, and that do exist being on ship.

Are the insulations upto this application? I hope it is a cast coil design. You may check up the insulation and the transformer data whether it has been designed for salt ambience.

Both transformers are pretty new. They retorofitted the ship in Mobile recently, went through sea trails and everything was peachy. Then at sea, this problem surfaced. Blew a hole in xform #1 large enough to put your fist in. Experienced secondary tripping on the 450 volt side. (Made a mistake, pri is 4160v). I don't have enough facts yet to give you good input, hope to next week. Ship is in Panama and to be in Texas soon.

Thanks for your input

I am in Panama right now. Need some eyes on the job?

I'll let you know!

Give me phone numbers and tell me what you do and what your doing down there. POC, Jim@seaboardcontrols.com

If you can get any details out of the protection relays the information will help to understand what went wrong. A few words of advice also - in the haste to get everything back on line & running a lot of valuable evidence is lost so try to preserve as much as possible early on.

Being a dry type they do need to be monitored carefully for high temperaturesa sthese can sometimes burn the insulation & create a fault. To have two go means that there could also be some harmonics creeping in which could give rise to additional heating. You seem to have N-1 some overloading is not a big factor in the first instance but could be in the second.

One last thing - look around for signs of vermin - some like the epoxies & varnishes on the transformers.

You remind me of me! Get the damned facts first, don't touch a thing and if you do, document what you have and what you're doing. You've been around awhile too I think!

Thanks

(By the way, I told them when they installed the rental transformer, put their fingers in their ears before they close the breaker!)

If the rental transformer craps out immediately, it won't likely be a problem with the transformer itself, but rather with some fault in the network it is feeding. (There shouldn't yet be vermin attack or salt contamination or even moisture issues in a new transformer.)

I'm curious about the overall picture. Why would there be medium-voltage generation and transformer(s) shipboard? The distances seem to be too small to create excessive voltage losses in a low-voltage (say 480) system.

Good question but I didn't design this ship. Copper, of course, is always a determining factor as there can be as much as a 15% loss from a 480 v system to a 600 v system. But, it is not uncommon for medium voltages to be used aboard ships!

Interesting! My involvement so far has been with fishing and processing vessels up to about 300 ft (100 m) long and about 1000 tons displacement. In that environment, medium voltage would be weird. Yes, there might be some savings in copper conductor size, but that would be offset by larger switchgear, transformers, and crew familiarity with MV. Larger ships maybe could justify this, however.

Been going to Sitka every year for the USCG s good to hear from you as I've enjoyed that last frontier of your beautiful country (opps, state) I've ran across weird voltages (to us) all the time and logic sometimes confuses me as I design switchgear and shipboard electrical systems but most in the US. Copper savings on larger ships are acceptable to me, on smaller, stupid! Most of us look at 480 volts (on smaller ships, OSV's) and the preverbial 440 v on foreign vessels. (Don't know why they use 440, more copper waste) In my 48 years in this business I have accepted the fact that my thought process is not always the same as others and I guarantee they have a reason to do what they do! Staying confused is part of being an electrical engineer. Hey, it's okay with me but something went wrong with international standards!

Thanks for talking with me as guys like you and I may straiten out some of of this BS

Jim Raub, Southeast Texas

oh, by the way, I made a mistake, pri voltage is 4160

Thank you and if I can help you in any way jim@seaboardcontrols.com and I would like to have yoru personel email, might throw some work your way. Check us out at seaboardcontrols.com and my cell is 985.519.5223.

Hello Friend,

It was very unfortunate for you to have this kind of problem. By the way and of course you will purchase at least one (1) 2500kVA transformer, while having a rented EDG.

Let's go back to your problem... " transformers tripped one at the time?" It was really unfortunate. A short circuit is a main culprit in it. Or.... 'an inside sobatage' hope not.

Question.

Do the two xfmrs housed in one area, if not... make a room for it complete with ventilation. Humidity or moist are your enemy, sometimes water splash, which you don't know may occur, this unmanned equipment. Some crew are putting canopy above the xfmr.

By the way, you can purchase dry type transformer/resin/encapsulated and installed inside NEMA 3R, this a safety measure for all ship aboard... read the SOLAS.

Eren

Any fault that impinges directly on ur transformer completely rules out the importance of ur protective systems. Its actually a sad situation that must be handled diligently and not being in a hurry. The transformer, being a dry type, should be thermally protected in addition to other protections.

Now, if I may ask, what were u using to power the transformers? Is the transformer a stepping down transformer? (pls. dont get disturbed the question)

Why do U need a 2500kw rental generator? Do u want to power directly?

Is the ship^,s generator rated for 13.8kv?

IF the above questions are in the affirmative, check ur LV cables and other load cables for shorts and start making arrangement to change ur protection relays. Also revisit ur earthing system to find out if any of the transformer is not properly bonded to earth or neutral earthing. Check if there is a broken earth/bonding wire.

Pls. do the above checks b/4 attempting to to put any alternative generator or transformer.

I would rather suggest U do the above checks and install a rental transformer to take u out of trouble waters rather than renting a generator that will be very costly.

Take care

Dickson