harmonics

[brian john]

Single phase applications as discussed here (I believe) where harmonics might be an issue are single phase derived from a 208/120 VAC 3 phase 4 wire wye.

My point is every one discusses harmonics to no end yet few have seen cases where harmonics are an issue and when the make statements about harmonics issues I would like to know how the harmonics resulted in problems.

I have investigated 100's of harmonic issues and of those maybe 15-20 were really related to harmonics, most were software, hardware, or wiring issues. Of the one's that were harmonic related most were while the site was connected to an on site generator.

 

[don_resqcapt19]

The problem with talking about harmonics is the fact that most of what most people "know" about harmonics has come from information that was provided by people or companies with an economic interest in solving the harmonic "problem".

 

[Besoeker]

My point is every one discusses harmonics to no end yet few have seen cases where harmonics are an issue and when the make statements about harmonics issues I would like to know how the harmonics resulted in problems.

I have seen, and had to deal with, cases where harmonics were a serious issue.
One in particular was in a very famous luxury hotel in the Middle East.
The cause of the problem was the extent of controlled lighting used (MWs) resulting in very high harmonic content and overloaded neutrals.
The problem was resolved by fitting passive harmonic filters.

Having said that, we usually deal with potential harmonic problems at the design stage by considering the impact of any new load on the distribution system and taking steps to mitigate any such problems.

 

[dbuckley]

I've been involved with four really serious harmonics issues over my time, one a discotheque with a burned up distribution panel and melted wiring, and that was in the 70s, when no-one knew anything about harmonics. After the replacement burned up as well a vastly oversize panel and feeder was installed, and that survived fine.

The second was a couple of City of London trading floors in one building, which had vertical enclosed busbars up the building, and the busbars were overheating (smoking...), and the cure for that was a K rated transformer on each of the trading floors.

The other two were data centres, but relatively old installations, but thats about what you would expect.

I've seen several other cases where the neutral current was (much) higher than the phase currents, but because the actual total load was much smaller than the installation was capable of, there was no overloading issue.

Bear in mind that for most of my working life I've not been professionally electrically involved in these sorts of problems, they have just occured where I happened to be working at the time; I've mostly been an IT boy. Thus if you do non-resi, you should expect to see neutral problems from time to time.