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Questions and Answers
How should a transformer react as far as heating and cooling itself with no help?
In liquid type transformers, hot oil rises to the top, goes into the radiators, cools down, sinks to the bottom, goes back into the transformer.
What causes heat in the transformers?
Losses build up heat in the cores and windings.
What are the two cooling classes for dry type transformers?
Forced air (FA) and ambient air (AA).
What does AA mean?
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What does FA mean?
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What can we use to cool down liquid type transformers?
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How do we use air to cool down liquid type transformers?
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How do we use water to cool down liquid type transformers?
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What are the types of radiators we have?
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What is the rule about coolers?
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How do coolers work?
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What do we use oil pumps for?
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Why do we use oil pumps?
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What does directed mean?
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What is a conservator?
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What does a conservator do?
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What is the result of not having a conservator?
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What are the two types of conservators?
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What is a sealed conservator?
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What is an open conservator?
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What is a free breathing transformer?
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What does the breather unit do?
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Are open conservators sucking in contaminants?
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What are the parts to a breather unit?
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What does the oil trap of a breather unit used for?
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What does the silica gel/desiccant do for a breather unit?
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How do we know when to replace silica gel/desiccant?
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When do we change out the silica gel/desiccant?
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Why do we need to replace the silica gel/desiccant before it reaches the top?
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What are dry type transformers sealed with?
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How do we cool a dry type transformer?
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What is convection?
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What are the types of tanks?
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If a bladder cannot be replaced what do you do?
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Study Notes
Transformer Heating and Cooling
- In liquid type transformers, hot oil rises, cools in radiators, and then returns to the bottom.
- Heat in transformers is generated from losses in cores and windings.
Cooling Classes and Methods
- Two cooling classes for dry type transformers: forced air (FA) and ambient air (AA).
- AA refers to a natural air cooling system without added cooling.
- FA enhances cooling by incorporating fans to circulate air through cooling ducts.
Cooling Liquids and Systems
- Cooling options for liquid transformers include oil, water, and air.
- Air cooling can be achieved using fans or naturally circulating air.
- Water cooling involves heat exchangers that circulate cold water alongside hot oil.
Radiators, Coolers, and Pumps
- Types of radiators include panel, tube, and coolers.
- Coolers operate continuously with pumps and fans for efficiency.
- Oil pumps are deployed to enhance oil circulation and expedite cooling.
Cooling Terminology
- Directed flow indicates a targeted pathway for oil movement.
- Definitions of key components:
- O: oil
- A: air
- N: natural
- F: forced
- D: directed
- W: water
Operational Classifications
- ONAN: Oil Natural Air Natural, no mechanical assistance.
- OFAF: Oil Forced Air Forced, combines circulating oil and fan cooling.
- OFWF: Oil Forced Water Forced, integrates oil movement with water cooling.
- Multi-stage cooling improves a transformer’s cooling capacity.
Transformer Tanks and Sealing
- Sealed tank transformers contain no breather unit, conservator, or gas bottle.
- Nitrogen blanketed transformers have a nitrogen system for pressure maintenance.
- Low pressure in sealed transformers requires the addition of nitrogen to sustain pressure.
Conservators
- A conservator serves as an expansion chamber for oil in transformers.
- Without a conservator, transformers cannot be filled to maximum oil capacity.
- Two types of conservators: open (no bladder) and sealed (with bladder).
Open vs Sealed Conservators
- Sealed conservators utilize an air-tight bladder to manage oil expansion and contraction.
- Open conservators feature a breather unit to regulate gas exchange without contamination.
- The breather unit prevents contaminants by using silica gel/desiccant and an oil trap.
Maintenance and Functionality
- Silica gel in breather units changes color as it absorbs moisture, indicating replacement is needed at 75% saturation.
- Dry type transformers are encased in materials like plastic, epoxy, or fiberglass.
- Cooling for dry transformers is achieved via fans that force air through winding gaps.
Convection and Tank Types
- Convection describes fluid movement driven by temperature-induced density variations.
- Various tank types include sealed, nitrogen blanketed, sealed conservator, open conservator, and free breathing configurations.
- If a bladder in a sealed conservator cannot be replaced, it can operate as an open conservator with a breather unit.
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Description
Explore the essential concepts of transformer cooling systems and conservators through these flashcards. Each card provides definitions and explanations about how transformers heat and cool themselves naturally, as well as the causes of heat in transformers.