Dry Type vs Liquid Filled Distribution XFMR

FaradayFF

Senior Member
Location
California
Greetings gentlemen,

What are some main advantages and highlights of dry type versus liquid filled xfmrs? We're talking 25kVA pad mount units. Eaton offers both units, I am just wandering in what applications you'd pick one over the other. Also, when would you recommend specifying built in fuses and surge arrestors?

Thank you for your responses.

Best Regards,
EE
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
liquid filled cool better but may need some way of dealing with potential leaks.

I don't it makes any real difference though for such a small transformer.

I am not a fan of fuses in general since it seems like there are never any spares available when one blows.

As for the surge restorers, that is mostly a design decision, which means it is usually based on lore, legend, and what someone decided 30 years ago and put in the spec, as opposed to any really good reasons.
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
questions...
Inside or outside?
Primary voltage?
can the primary be breaker protected or is this MV application.
EE, what are you designing?
 

Besoeker3

Senior Member
Location
UK
Greetings gentlemen,

What are some main advantages and highlights of dry type versus liquid filled xfmrs? We're talking 25kVA pad mount units. Eaton offers both units, I am just wandering in what applications you'd pick one over the other. Also, when would you recommend specifying built in fuses and surge arrestors?

Thank you for your responses.

Best Regards,
EE
At 25kVA I'd use air cooled for indoor applications. Outdoors I'd go oil filled.
 

FaradayFF

Senior Member
Location
California
questions...
Inside or outside?
Primary voltage?
can the primary be breaker protected or is this MV application.
EE, what are you designing?
This XFMR would be located outside, but away from direct sunlight, since it would be partially enclosed. Primary voltage is 12.5kV, the xfmr is currently protected by pole mounted fuses on the primary which feed the transformer. It is a "simple" distribution system for a facility with a backup genset. Since the setup would be located at a higher elevation, I think adding surge arrestors to the spec would be a good idea.

Thanks,
EE
 

Besoeker3

Senior Member
Location
UK
This XFMR would be located outside, but away from direct sunlight, since it would be partially enclosed. Primary voltage is 12.5kV, the xfmr is currently protected by pole mounted fuses on the primary which feed the transformer. It is a "simple" distribution system for a facility with a backup genset. Since the setup would be located at a higher elevation, I think adding surge arrestors to the spec would be a good idea.

Thanks,
EE
Then I would go for oil filled. Air cooled would need ventilation and some means of preventing the ingress of moisture.
 

paulengr

Senior Member
Built in fuses on the primary side are almost always Bay-O-Net which are oil immersed. Surge arresters will be external to the tank. Best though is to put them on the pole right next to it but make your connections as short as possible. See articles on arresterworks.com for illustrations and explanations why. You don’t want a failed arrester dumping hot slag and an arc into your oil filled tank. If it’s pad mount with a riser (underground) feed though it will be cheaper and safer to use elbow connectors on the 12.47 kV side. You can get the lightning arrester and even the fuse as accessories that go inside the elbow connector. You can get the elbow as a rated disconnect too so no need to mess with a cutout. Alternatively if you are feeding from a pole I’d just do pole mount everything and not bother with the pad. Leave the 12.47 kV stuff out in the open where it is easy to inspect and out of harms way.

This makes everything interchangeable and easy to service. Cooper and ABB (T&B) are the big names in IEEE 386 elbow connectors with massive catalogs of options.


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FaradayFF

Senior Member
Location
California
Built in fuses on the primary side are almost always Bay-O-Net which are oil immersed. Surge arresters will be external to the tank. Best though is to put them on the pole right next to it but make your connections as short as possible. See articles on arresterworks.com for illustrations and explanations why. You don’t want a failed arrester dumping hot slag and an arc into your oil filled tank. If it’s pad mount with a riser (underground) feed though it will be cheaper and safer to use elbow connectors on the 12.47 kV side. You can get the lightning arrester and even the fuse as accessories that go inside the elbow connector. You can get the elbow as a rated disconnect too so no need to mess with a cutout. Alternatively if you are feeding from a pole I’d just do pole mount everything and not bother with the pad. Leave the 12.47 kV stuff out in the open where it is easy to inspect and out of harms way.

This makes everything interchangeable and easy to service. Cooper and ABB (T&B) are the big names in IEEE 386 elbow connectors with massive catalogs of options.


Sent from my iPhone using Tapatalk
Thanks!
 
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