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Are you planning to store a transformer before it is powered up? How to store your transformer so it’s ready to use when needed.
Are you planning to store a transformer for a long time before it is energized?
This article will guide you on when, where, how, and what to store transformers. We cover distribution transformers under 69kV.
When Should I Consider Long-Term Storage?
You need to have a plan if you intend to store a transformer for more than 6 months.
What Is the Best Place to Store My Transformer?
The location is the key to a reliable and efficient storage plan. Backup units should be located…
- Rapid deployment is possible near the installation site
- When possible, keep your dry-types under cover (especially if you can).
- Temperature fluctuations are not extreme
What Type of Transformers Should I Store?
Both sealed liquid-filled and vented dry-type transformers require long-term storage. Both can be stored for long periods of time, but maintenance is different for each. We’ll look at the and of both transformer types.
How to Store Transformers
Transformers with liquid-filled tanks
Substation transformers and padmount are designed to be installed outdoors. The sealed tank allows for easier storage and maintenance.
Four keys are needed to store liquid-filled transformers.
- Keep the nitrogen blanket between 2-3 psi
- Store transformers in their factory-filled oil
- Avoid extreme temperature changes
- Test for acceptance and maintenance at the end the storage period
We’ll explore these four points in more detail…
Monitor Nitrogen Levels
All transformers, both new and reconditioned, are shipped with a nitrogen-pressurized blanket. The typical values are between -2 and +5 psi. For long-term storage, the nitrogen blanket should have a positive charge. Fill the Nitrogen Port to 2-3 psi if the gauge is negative. Before storing, ensure that the pressure is maintained for at least 8 hours.
Check the gauge regularly to make sure it is reading between 2 and 3 psi. We recommend checking transformers every quarter to ensure that nitrogen levels are monitored at different temperatures.
Ideal pressure should be kept on the unit. Negative pressure can occur if the unit is stored in a place where temperatures are very variable. A high desert would be an example where daytime and evening temperatures are very different.
It is less important, however, that the unit is always under positive pressure. What is more important is that it can hold both negative and positive pressure.
The lowest pressure is 0. You might have an air or oil leak in your transformer if it remains at 0. Look at the article about leak troubleshooting.
Oil Levels
Electrical Transformer Buyers transformers are shipped with the correct amount of Transformer Oil. The oil in the unit should be kept there during storage. Check the oil levels before installation.
Testing
After the storage period is over, run standard acceptance and maintenance tests. Before putting into service, any unit that has been stored for a long time should be tested.
A minimum testing protocol should include TTR (aka Megger), insulation resistance, and winding resistance.
Low megger readings may indicate moisture in transformer fluid.
It is recommended that you test the oil to determine its moisture content before returning a spare part to service.
Store Liquid-filled Units Inside
It is possible to store liquid-filled transformers indoors (and this happens quite often), but it is not required. Electrical Transformer Buyers, for example, keep hundreds of liquid-filled transformers outdoors year-round. We don’t plan to store units for longer than a year, but end users who want a critical spare transformer on hand might end up keeping them for decades.
Some end users believe that the best place to store liquid-filled transformers is indoors.
The transformer should be completely shielded from the weather to prevent the paint from deteriorating. It will also help slow down the degrading of rubber and plastic components such as gaskets, gauges, and certain types of bushings.
Here are some tips to consider if you plan on storing your liquid-filled transformer inside…
- Floor Capacity: The majority of standard warehouse floors are 3-4″ thick concrete slabs, which can easily crack when heavier liquid-filled units are placed on them. It is important to first check the weight capacity of the floor and ensure that it can support the weight of a transformer, plus the forklift.
- Environmental implications Oil-filled liquid transformers are large tanks. It is important to consider the insurance and environmental implications of having so much oil inside in case of a fire or leak.
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UV Rated Substation Components
When storing transformers outside, it is important to keep in mind that unit substation transformers are the best option.
Check with the manufacturer if you intend to store an outdoor unit transformer.
The bushings and gauge face plates of a substation transformer that was designed for indoor usage may not be suitable for long-term storage under direct sunlight. The gauge face plates and bushings may become fogged up over time like an old car’s headlights.
If a transformer has bushings at the top of the unit, they’re UV-rated and meant to be exposed. If the bushings are on the side of a transformer but are in a sealed air-terminal chamber they are not meant to be exposed to direct sunlight and will eventually lose their insulation properties.
You may find a solution by shrink-wrapping these bushings or inventing some other method to seal them up.
Reconditioning spare transformers before deployment
You may want to have a transformer repair company recondition your transformer if you’ve had it stored for more than a decade. This is a great way to…
- Gaskets can degrade over time. Older transformers often experience gasket failures.
- It will prevent rust by applying a new protective coating.
- This report is updated on all electrical and oil tests.
- The warranty should be renewed so that the transformer remains covered during the most critical stage of its life, at the beginning.
Please contact us for a quote on reconditioning an old transformer.
Dry-type transformers
Dry-type transformers require special storage because they are not sealed.
Check the list below for proper storage of dry-type transformers.
- Keep all internal components, including windings and inner components, dry and dust-free.
- When possible, store your items in a climate-controlled building.
- Store outside? Cover your items with a tarp
- Keep the enclosure clean and free from dust, debris, and critters
- Test transformers at the end the storage period. ( Read about transformer testing).
Keeping your transformer dry
The vented enclosure makes the dry-type windings more susceptible to moisture. Keep the transformer properly ventilated and dry for long-term storage. It is best to do this in a building with a controlled temperature. Desiccant packs and/or space heaters can help to remove moisture from an enclosure. Check the desiccant packets at regular intervals. A tarp can be used to protect outdoor units.
Cleaning the enclosure
Dry transformers have vents that allow dirt, debris, and rodents to enter. Regular cleaning of the enclosure should be part of any long-term storage plan. Rodent screens can be used to close vents if the unit will be stored in an area where animals may be a problem.
Testing
Before putting dry transformers in service, perform standard maintenance and acceptance testing. Test the windings for moisture.
How can I tell if my transformer has dried out enough?
It is a question that comes up often when it concerns storing dry types. A Megger test can be used to determine the insulation resistance. Transformers that are well insulated should have a measurement of at least 1MO for each volt. A reading of 500MO is acceptable for a unit with 480 volts.
It is not enough dry if your transformer shows a reading of less than this. Dry types larger with high moisture levels may require curing. Electrical Transformer Buyers has bake-out ovens to remove moisture. Please fill out this form to request this.
Conclusion
Storing spare transformers can be a great way to be prepared for the unexpected. To ensure that your transformer will be ready to use when you need it, follow the steps listed in this article.
Electrical Transformer Buyers‘s customers are always our top priority. We stock thousands of transformers and have the fastest lead times in the industry. We ensure that you receive what you need when you most need it. If you are in need of a transformer, please fill out the form and a representative will contact you within an hour.