When to Replace Distribution Transformers

It depends on the actual pricing of the transformers. And once manufacturers of the better transformers (or higher grade materials) recognize a captive audience, you can expect prices to rise. (Prices will probably rise both appropriately due to increased demand, but also somewhat influenced by the "captive audience" aspect.)

I am not sure what the going rate for a good quality 2500 KVA transformer is but as I understanding now transformers in that size range are already in the high 90%'s efficiency range.

Picking up another theoretical 1/2% to 2% efficiency and using that to offset the purchase costs of a new unit doesn't seem like a wise idea to me.

IF the old one is not large enough or burned out then yes certainly putting in a newer higher efficiency unit would be wise but until then it seem more like tossing good revenue at a problem that doesn't exist anywhere but on paper.

I concur. Furthermore, it is not just the cost of the new transformer, but also the cost of the outage, and in some cases, the cost of physically maneuvering the old one out & the new one in place that has to be considered, busbar/cable work, etc.

We just had to go through this by way of upgrading the original 1500KVA to a 2500KVA with the new facilities we are building and needed the extra power. We did not own either transformer. The Utility company owns the distribution transformers so there was no cost to us for the transformer. However they made a fortune relocating new poles and new wires due to original poles being in the middle of the new buildings. And we are maxed out power wise. Next step for additional facilities, we have to install a sub station, or go cogen. If we go cogen, the utility will take back their 2500KVA. We will be off their grid at that point. I don't know if this is typical, but in my area, all utilities own all distribution XMR's 1000KVA and up.

This is not quite correct. The DOE »10 CFR Part 431« Rule on distribution transformers provides a graded efficiency scale depending primarily on rating. For DRY-TYPE transformers, the specified efficiency varies from: 98.62% @ 10 kVA to 99.49% @ 833 kVA for single phase units, and 988.36% @ 15 kVA to 99.49% @ 2,500 kVA for three-phase units. For oil-filled transformes, the specifed efficiency varies from: 98.10% @ 15 kVA to 99.31% @833 kVA for single-phase units, and 97.50% @ 15 kVA to 99.31% @ 2,500 kVA for three-phase units. These efficiencies apply ONLY to NEW PURCHASES. There is no guidance provided as to the retirement of existing transformers that would be considerably less efficient. No doubt, . . . the older the transformer - the less efficient it is likely to be. Without knowing the efficiency of a transformer the owners of the transformer can not determine when it would be appropriate to replace it with a new one - a more efficient one. The owners of transformers do not have the equipment not the trained personnel to go out and measure the efficiency of their transformers. Also, such test equipment is not readily portable and the measurement of the efficiency will require an outage - something that difficult to arrange. Having the above in mind, I developed a readily portable (weighing in at <30 pounds) test equipment for assessing the efficiency of such distribution transformers. To my surprise I found no instrument manufacturer eager to produce the test set, . . . nor a utility eager to use such an instrument to assess the efficiency of their distribution transformers. Oleh

better efficiency is good, but doesn't it also come with the added cost of protection schemes for the transformers i.e relays, ct's and the works? is the cost really worth the upgrade for a 1/2 % boost? And most importantly WHAT WILL HAPPEN TO THE INFRUSTRUCTURE IN THE EVENT OF A MAJOR FAULT? ANOTHER 911