Using Dry Type Trasformer Outdoors

[mull982]

I wanted to hear any feedback or experiences from others regarding the use of Dry Type Transformers in outdoor locations. I'm trying to convince some folks who wish to use a dry type 2500kVA 13.8kV-480V in an outdoor location that they should consider an oil filled transformer instead.

From what I have read the only dry type transformer that may be adequate to use outdoors is a Cast Coil type transformer. A VPI or VPE transformer is not suited for an outdoor location even with a NEMA 3R enclosure. The concern with the dry types outdoors seems to be with moisture penetrating the insulation.

Does anyone have experience (good or bad) with using dry types outdoors?

 

[templdl]

I wanted to hear any feedback or experiences from others regarding the use of Dry Type Transformers in outdoor locations. I'm trying to convince some folks who wish to use a dry type 2500kVA 13.8kV-480V in an outdoor location that they should consider an oil filled transformer instead.

From what I have read the only dry type transformer that may be adequate to use outdoors is a Cast Coil type transformer. A VPI or VPE transformer is not suited for an outdoor location even with a NEMA 3R enclosure. The concern with the dry types outdoors seems to be with moisture penetrating the insulation.

Does anyone have experience (good or bad) with using dry types outdoors?

This is a loaded question. Remembering that the dry type transformers are ventilated and you have a MV primary the MV is an issue depoernding upon the climate which you haven't indicated. Rain getting into the transformer must me addressed. In snowy Climates, snow blowing into the transformer can be a concern with either a MV or even a LV transformer.
Dry type transformers with as LV primary, 600v and below, do have a weather shield option which is not offered with those having a MV primary. Someimes even transformers with a LV pri. that have weather shields don't fair well in snowy climates as the vents still can clog up with snow.
I wouilkd suggest a liquid type transformer for your application which are often less expensive that the DTDTs as I recall.

 

[big john]

Not a fan.

Water always gets in. And even without that, they are great at sucking up humidity. It's nothing for me to test an exterior dry type and see power-factor approaching 10%.

Seen several of them blow up because of precipitation ingress during storms.

If someone is concerned about oil, use a dry type but at least build a climate-controlled blockhouse around the stupid thing. Or get an oil filled and look into the environmentally friendly FR3 and Envirotemp fluids.

 

[zog]

I agree with Big John, use either liquid or cast coil.

 

[mull982]

Thanks guys we are pushing for the use of oil filled unit.

Also curious to hear thoughts on the use of heaters in outdoor Switchboards. In addition to the transformer this outdoor unit sub will also consist of an enclosed 15kV breaker and 480V Switchboard. 15kV breaker has internal heaters which I typically see on outdoor MV equipment but am not sure about the need for heaters in outdoor LV equipment.

Does a 3000A Switchboard in a 3R enclosure outdoors require space heaters? I have never seen heaters in an outdoor panelboard so was just curious when they should be used.

 

[templdl]

Thanks guys we are pushing for the use of oil filled unit.

Also curious to hear thoughts on the use of heaters in outdoor Switchboards. In addition to the transformer this outdoor unit sub will also consist of an enclosed 15kV breaker and 480V Switchboard. 15kV breaker has internal heaters which I typically see on outdoor MV equipment but am not sure about the need for heaters in outdoor LV equipment.

Does a 3000A Switchboard in a 3R enclosure outdoors require space heaters? I have never seen heaters in an outdoor panelboard so was just curious when they should be used.

The concern is if the gear is continually energized and capable of generating its own heat in order to keep the RH about 65% or below.
Space heaters are used to cause the air to convect and move which reduces the opportunity for moisture to condense on the electrical components. It has been found that the simple increase in the ambient temp by 10deg is enough to affectively reduce the RH to an acceptable level.
Space heaters can be left on continually, controlled by a N/O contact which simply closes when the gear has been deenergized or with a t-stat. . Space heater wattagages are often available from 100-350w each and are located in the bottom area of the enclosure. They usually consist of a simple resistor mounted is a sheet metal enclosure witn a bunch of holes punched in it. Nothing complex at all.

 

[jim dungar]

Does a 3000A Switchboard in a 3R enclosure outdoors require space heaters? I have never seen heaters in an outdoor panelboard so was just curious when they should be used.

Heaters are most often used during periods of little to no-load, to manage condensation.
If loaded equipment is likely to be 'turned off suddenly' when condensation can form, heaters (with an alternate power supply) should be used.

True case: Middle of winter, outside temp below 0F. Utility dumps the power grid. Equipment heaters were not fed from alternate source.
When utility power was finally restored there was a flash over of the insulators. It took several more days to get facility back into operation.

 

[mull982]

The concern is if the gear is continually energized and capable of generating its own heat in order to keep the RH about 65% or below.
Space heaters are used to cause the air to convect and move which reduces the opportunity for moisture to condense on the electrical components. It has been found that the simple increase in the ambient temp by 10deg is enough to affectively reduce the RH to an acceptable level.
Space heaters can be left on continually, controlled by a N/O contact which simply closes when the gear has been deenergized or with a t-stat. . Space heater wattagages are often available from 100-350w each and are located in the bottom area of the enclosure. They usually consist of a simple resistor mounted is a sheet metal enclosure witn a bunch of holes punched in it. Nothing complex at all.

The Switchboard will be continually energized but there may be times at night where there is little to no load on the Switchboard. This will be a new Switchboard so right now I'm just considering weather or not to specify heaters in this new Switchboard.

 

[zog]

The Switchboard will be continually energized but there may be times at night where there is little to no load on the Switchboard. This will be a new Switchboard so right now I'm just considering weather or not to specify heaters in this new Switchboard.

You know heaters are like a couple hundred bucks to add right? How much is a new switchboard?

 

[templdl]

The Switchboard will be continually energized but there may be times at night where there is little to no load on the Switchboard. This will be a new Switchboard so right now I'm just considering weather or not to specify heaters in this new Switchboard.

Add the heaters and thermostats which is done alll of the time and call it a day. Don't agonise over it if you should or not.

 

[Haji]

Wonder why manufacturer of outdoor 480V panel board has not included space heater in the panel in the first place.