Medium Voltage Substation vs Pad-mount Transformers

[CuriousElectron]

Hi Guys,
Are there any application guidelines for when you'd use a Substation transformer versus a standard pad-mount unit? My understanding is that substation transformer is typically a higher quality product, are there any other differences between them application-wise?

Thanks,
EE

 

[bacon4life]

It might depend on what you define as substation. Some of my customers purchase "substations" consisting of a skid mounted 1 MVA 15 kV/480V transformer and a 480 V panel board.

There is not much size overlap between C57.12.10 and C57.12.22. We routinely have regular pole/padmounted transformers inside of substations to provide station service.

C57.12.10-1997 American National Standard for Transformers--230 kV and Below 833/958 through 8333/10 417 kVA, Single-Phase, and 750/862 through 60 000/80 000/100 000 kVA, Three-Phase without Load Tap Changing; and 3750/4687 through 60 000/80 000/100 000 kVA with Load Tap Changing--Safety Requirements

C57.12.22-1993 (R1998) American National Standard for Transformers-- Pad-Mounted, Compartmental-Type, Self-Cooled, Three-Phase Distribution Transformers with High-Voltage Bushings, 2500 kVA and Smaller: High-Voltage, 34 500 GrdY/19 920 Volts and Below; Low Voltage, 480 Volts and Below--Requirements

 

[cuky2000]

Unit substation transformer and pad-mounted unit are both available with similar capacities and primary voltage range. The ancillary component such as protective devices is separated from the unit while for pad mounted the
protective devices such as fuses are built-in the transformer. Also, the primary Connection & optional Surge arrester are connected with elbow connectors, operated with a hot stick.

It appears that the unit substation is more robust in construction than the pad-mounted transformer.

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[argotier]

In regards to application, I had the idea that, with same technical data, the padmounted transformer was more suited for "public" or unguarded locations, while substation transformers needs always to be located in closed or restricted areas.

I don't know where I got this idea, could be somewhat true? There is some ground to it? (I'm not really familiar with ANSI world)