Transformer Cooling Systems Flashcards

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?

Natural air system. Signup and view all the answers

What does FA mean?

We add fans to the bottom and force air up through the vertical cooling ducts on the winding. Signup and view all the answers

What can we use to cool down liquid type transformers?

Oil, water, air. Signup and view all the answers

How do we use air to cool down liquid type transformers?

Fans, we can force air across the radiators or we can use natural air. Signup and view all the answers

How do we use water to cool down liquid type transformers?

Heat exchangers, circulating cold water through tubes and hot oil through the transformer. Signup and view all the answers

What are the types of radiators we have?

Panel, tube, coolers. Signup and view all the answers

What is the rule about coolers?

They must have the pumps and fans operating 24/7 to be able to function. Signup and view all the answers

How do coolers work?

Oil runs through thin sheets while fans are blowing across them. Signup and view all the answers

What do we use oil pumps for?

Force oil through the transformer or speed up the circulation process. Signup and view all the answers

Why do we use oil pumps?

To cool oil faster. Signup and view all the answers

What does directed mean?

We have a specific area or we are trying to pinpoint where the oil is going to flow into. Signup and view all the answers

What is a conservator?

Expansion chamber for our oil. Signup and view all the answers

What does a conservator do?

When oil heats up, the conservator gives it area or space to expand into. Signup and view all the answers

What is the result of not having a conservator?

We are unable to fill our transformer up to the very top with oil. Signup and view all the answers

What are the two types of conservators?

Open and sealed. Signup and view all the answers

What is a sealed conservator?

Conservators with a bladder or diaphragm. Signup and view all the answers

What is an open conservator?

No bladder, has a breather unit that allows gas and air to enter and leave the transformer. Signup and view all the answers

What is a free breathing transformer?

No conservator, just has a breather unit attached to the transformer. Signup and view all the answers

What does the breather unit do?

Pushes and pulls air from the outside into the transformer. Signup and view all the answers

Are open conservators sucking in contaminants?

False Signup and view all the answers

What are the parts to a breather unit?

Silica gel/desiccant and oil trap. Signup and view all the answers

What does the oil trap of a breather unit used for?

To catch contaminants, dust, particles, foreign objects. Signup and view all the answers

What does the silica gel/desiccant do for a breather unit?

Removes any moisture. Signup and view all the answers

How do we know when to replace silica gel/desiccant?

It changes color. Signup and view all the answers

When do we change out the silica gel/desiccant?

75%. Signup and view all the answers

Why do we need to replace the silica gel/desiccant before it reaches the top?

That means we are not filtering out moisture. Signup and view all the answers

What are dry type transformers sealed with?

Plastic, epoxy, fiberglass. Signup and view all the answers

How do we cool a dry type transformer?

Use fans to force air upwards through the gaps of the layers and windings. Signup and view all the answers

What is convection?

The movement of fluids based upon density which is a direct cause of temperature. Signup and view all the answers

What are the types of tanks?

Sealed, N2 blanket, sealed conservator, open conservator, free breathing. Signup and view all the answers

If a bladder cannot be replaced what do you do?

Attach a breather unit and allow it to operate as an open conservator unit. Signup and view all the answers

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.