Compare old to new transformer losses
Compare old to new transformer losses
(OP)
I am searching for a way to determine the losses on 40 year old Federal Pacific 1000kVA 13.8kV - 480 delta delta transformers in order to compare them to a new modern transformer. A saving in operating cost could justify replacing the 14 FPE transformers with new Delta Wye units.
There are 14 transformers in groups on various 13.8KV circuit. An example is one circuit with four transformers on the same 13.8kV feeder. there is no metering on each transformer primary only the Eaton IQ4000 at the 13.8kV breaker. The load on each transformers is approximately a 500 amp steady load. This has been the loading for the entire life of the transformers.
Is there a way to determine the losses on one transformer?
The four single ended unit substations have tie breakers and a bus tie between them and can be paralleled to share load and one if the four transformers can be unloaded.
Any ideas? Thank you in advance.
There are 14 transformers in groups on various 13.8KV circuit. An example is one circuit with four transformers on the same 13.8kV feeder. there is no metering on each transformer primary only the Eaton IQ4000 at the 13.8kV breaker. The load on each transformers is approximately a 500 amp steady load. This has been the loading for the entire life of the transformers.
Is there a way to determine the losses on one transformer?
The four single ended unit substations have tie breakers and a bus tie between them and can be paralleled to share load and one if the four transformers can be unloaded.
Any ideas? Thank you in advance.






RE: Compare old to new transformer losses
RE: Compare old to new transformer losses
And to DTR2011 - To satisfy the curiosity of someone who doesn't have a lot to do with arc flash studies, what is the effect of a more efficient transformer on arc flash?
RE: Compare old to new transformer losses
I really can't imagine that the loss savings would pay for replacing the transformer over whatever the remaining life of the old transformer is.
RE: Compare old to new transformer losses
If you are determined to do this the hard way and actually measure the losses then a rental generator makes a good and relatively cheap high current injection source. You'll need to substitute a small DC power supply in lieu of the AVR so you can directly control the field in order to vary the voltage from zero up to rated, and the set needs to be rated for whatever current you need. Don't undersize the shorting bars.
RE: Compare old to new transformer losses
I agree with you that there would not be much of a pay back based on losses. The issue is what is the remaining life of the old transformers and how does one justify replacement prior to failure that will cause production down time.
These plant have no trouble upgrading production equipment to the latest greatest and power them with 45 year old ungrounded transformers!!!!
I suppose there is some justification for eliminating the ungrounded secondary for a solidly grounded WYE. They have experienced drive and production computer equipment issues.
Dan
RE: Compare old to new transformer losses
RE: Compare old to new transformer losses
RE: Compare old to new transformer losses
The justification has been well understand since the 1960s. Since you have an ungrounded 480 V system now, conversion to a high-resistance ground 480 V system would change virtually nothing in terms of operations, yet greatly help to reduce voltage transients. This will in turn, reduce motor insulation failures. I'd recommend looking into to that option.
As to your original question on losses, I think the best option is to try to find typical losses for transformers of that size and vintage and then compare to new units. Keep in mind that efficiency is something you pay for - manufacturers can improve efficiency by various methods, if you are willing to pay the price.
But I don't think increased efficiency is going to give you a lot of ammunition for replacement. A 40 year old 1000 kVA transformer is at end-of-life and I'm sure it is fully depreciated. I'd focus on:
Cost of downtime in the event of a transformer failure (it's when not if)
Reduced equipment insulation failures by converting from ungrounded delta to some type of grounded wye
Safety