Stadium Lighting

[mshields]

Doing work on a large outdoor stadium's lighting sports lighting system. What they've got now strikes me as a bit unusual. But given my experience with similar facilities (nil), what do I know.

Anyway, they've got 13.8kV comming into the facility. They transform via a single transformer to 2400V. There are two 2400 contactors that each feed 4 2400V to 480Y/277V transformers. The lighting is at 277V.

So these 8 transformers are normall de-energized. When they power up for a night game, they close the two 2400V contactors and it's "play ball".

All of the transformers involved are liquid filled.

My questions are these:

What's the advantage of the intermediate voltage of 2400V. Why not just distribute at 13.8kV and have your contactors at 13.8kV?

Should I care that the 2400V system sees the inrush from 8 - 225KVA transformers every time the lights go on. It's been working for 25 years just fine. But if we re-designed, I'm wondering what the best approach would be.

Any thoughts?


Mike

 

[72.5kv]

The cost of 15Kv class cables and switchgears to distribute at 13.8kv this could have been a deciding factor. The price jumps up going from 5Kv to 15Kv rated

 

[72.5kv]

Your point is very interesting. It would have made sense to pull the 13.8Kv to each of the eight transformers, but in most cases poco untimately decide based on your given load what voltage your service will be at. When I interned at a poco, to get primary distribution, you had to present a load over 7.5MVA this was at 12.47/7.2Kv. Below that point its 4.16/2.4kv.

 

[mxslick]

The best approach is...

The best approach is...

<snip>..........It's been working for 25 years just fine. But if we re-designed, I'm wondering what the best approach would be.

Any thoughts?


Mike

Mike, IMHO the best approach is NOT to re-design. If it's worked well for 25 years, why mess with it? I'm willing to bet that even a modern replacement contactor (or transformer for that matter) won't last as long. Most of the new gear is, well since this is a family-rated forum let's say not up to the standards of even 20 years ago.

An analogy from my primary trade: 35mm cinema projectors haven't changed at all in thier basic design since T. Edison invented them way back in the late 1800's. Several manufacturers over the years (most all long gone) tried some new technical "trick" to improve the way it works. Not only did cost go up, way up, (and this is a high-markup trade anyway) but the reliability went down.

I currently own one of the first-generation Simplex XL projectors, it is over 55 years old and runs quieter and steadier than the ten year old projectors at my University screening room!!

Now of course the studios want to go to Digital Cinema, replacing a proven, reliable technology (and solid product distribution system) with projectors at literally 50 times (!) the cost of 35mm and cinema computer servers that crash more often than early Windows systems!!

Ain't technology grand?

 

[iwire]

If it's worked well for 25 years, why mess with it?

I could list a lot of reasons why but I will stick with the one I consider pretty important.

I make my living installing electrical equipment and Mike makes his living designing electrical installations.

If a customer wants new equipment I will be the last person to slow them down.

Of course I still use a drill owned by my dad from the 60s and one of my PCs is about 8 years old which in PC time is a dinosaur.

 

[mxslick]

Good points..and I now see why a redesign might be the way to go in that case.

But my opinion comes from the fact I make far more money repairing/rebuilding old equipment than installing new equipment.

All depends on what we do for a living, eh?

 

[iwire]

All depends on what we do for a living, eh?

Yes I guess it does.

But if the old stuff is that good you should not have any work. :wink:

I actually agree with you for the most part, I still run into magnetic ballasts that are 30 or 40 years old.....if I find one electronic ballast more then 10 years old I will be surprised....planed obsolescence from the manufacturers.