The conservator contains an expandable bladder or diaphragm between the oil and air. Air enters and exits the space above the bladder/diaphragm as the oil level in the main tank goes up and down with temperature.
Showing posts with label Power Transformer. Show all posts
Showing posts with label Power Transformer. Show all posts
Main components of a power transformer
Main components of a power transformer can be categorize as follows.
1. Transformer tank
2. HV\LV Bushings
3. Conservator tank
4. Heat exchanger
5. Pressure relief device
6. Fire fighting system
7. Buchholz relay and other protection relays
8. Oil Treatment System
Additional Construction Features of a Power Transformer,
Carbon Dioxide (CO2) Fire Fighting System
CO2 fire fighting system Fire extinguishing system for two main transformers and two generators The fire extinguisher is commonly be used for two sets of main transformers and two sets of generators and detect fire inside the transformer room and generator housing instantaneously and accurately, and automatically discharge carbon dioxide gas to minimize damage of transformers and generators.
Oil Treatment System
One oil storage tank and one set of oil treatment system. The spare oil tank is used for storing spare insulation oil for transformers, and oil treatment system is used for refreshment of insulation oil of main transformers. Components of system: Oil storage tank, Piping system, Oil purification equipment, Oil tank for maintenance
CO2 fire fighting system Fire extinguishing system for two main transformers and two generators The fire extinguisher is commonly be used for two sets of main transformers and two sets of generators and detect fire inside the transformer room and generator housing instantaneously and accurately, and automatically discharge carbon dioxide gas to minimize damage of transformers and generators.
Oil Treatment System
One oil storage tank and one set of oil treatment system. The spare oil tank is used for storing spare insulation oil for transformers, and oil treatment system is used for refreshment of insulation oil of main transformers. Components of system: Oil storage tank, Piping system, Oil purification equipment, Oil tank for maintenance
Power Transformer- Cooling Methods- Internal Cooling
Internal Cooling
The heating of the coils depends on their thermal conductivity, which is itself a function of
• Thickness of the winding
• External insulation
A coil design, which allows the copper heat to flow radially outwards with little cross insulation in the path of the flow, leads to economical rating in that a high current density can be employed for a given temperature rise without sacrifice of efficiency.
The heating of the coils depends on their thermal conductivity, which is itself a function of
• Thickness of the winding
• External insulation
A coil design, which allows the copper heat to flow radially outwards with little cross insulation in the path of the flow, leads to economical rating in that a high current density can be employed for a given temperature rise without sacrifice of efficiency.
Power Transformer- Cooling Methods-Forced Oil Cooling
Forced Oil Cooling
When forced cooling becomes necessary in large high-voltage oil-immersed transformers.
The choice of the method of cooling will depend largely upon the conditions obtaining at
the site. Air-blast cooling can be used, a hollow-wailed tank being provided for the transformer and oil, the cooling air being blown through the hollow space. The heat removed from the inner walls of the tank can be raised to five or six times that dissipated naturally. A cheap method of forced cooling where a natural head of water is obtainable is the use of a cooling coil, consisting of tubes through which cold water is circulated, inserted in the top of the tank. This method has, however, the disadvantage that it introduces into the tank, system containing water under a head greater than that of the oil. Any leakage will be from the water to the oil, so that there is a risk of contaminating the oil and reducing its insulating value.
When forced cooling becomes necessary in large high-voltage oil-immersed transformers.
The choice of the method of cooling will depend largely upon the conditions obtaining at
the site. Air-blast cooling can be used, a hollow-wailed tank being provided for the transformer and oil, the cooling air being blown through the hollow space. The heat removed from the inner walls of the tank can be raised to five or six times that dissipated naturally. A cheap method of forced cooling where a natural head of water is obtainable is the use of a cooling coil, consisting of tubes through which cold water is circulated, inserted in the top of the tank. This method has, however, the disadvantage that it introduces into the tank, system containing water under a head greater than that of the oil. Any leakage will be from the water to the oil, so that there is a risk of contaminating the oil and reducing its insulating value.
Power Transformer- Cooling Methods-Natural Oil Cooling
Natural Oil Cooling
The oil in the ducts, and at the surface of the coils and cores, takes tip heat by conduction,
and raises cool oil from the bottom of the tank rising to take its place. A continuous circulation of oil is completed by the heated oil flowing to the tank sides where cooling to the ambient air occurs and falling again to the bottom of the tank. Oil has a large coefficient of volume expansion with increase of temperature, and a substantial circulation is readily obtained so long as the cooling ducts in the cores and coils are not unduly
restricted.
The oil in the ducts, and at the surface of the coils and cores, takes tip heat by conduction,
and raises cool oil from the bottom of the tank rising to take its place. A continuous circulation of oil is completed by the heated oil flowing to the tank sides where cooling to the ambient air occurs and falling again to the bottom of the tank. Oil has a large coefficient of volume expansion with increase of temperature, and a substantial circulation is readily obtained so long as the cooling ducts in the cores and coils are not unduly
restricted.
Power Transformer- Cooling Methods -Mixed Cooling
Mixed Cooling
ON/OB: As ON, but with alternative additional air-blast cooling.
ON/OFN, ON/OFB, ON/OFW, ON/OB/OFB, ON/OW/OFW: Alternative cooling
conditions in accordance with the methods indicated. A transformer may have two or three
ratings when more than one method of cooling is provided.
ON/OB: As ON, but with alternative additional air-blast cooling.
ON/OFN, ON/OFB, ON/OFW, ON/OB/OFB, ON/OW/OFW: Alternative cooling
conditions in accordance with the methods indicated. A transformer may have two or three
ratings when more than one method of cooling is provided.
Power Transformer- Cooling Methods
Simple Cooling
AN: Natural cooling by atmospheric circulation, without any special devices. The
transformer core and coils are open all round to the air. This method is confined to very small units at a few kV at low voltages.
AB: The cooling is improved by an air blast, directed by trunking and produced by a fan.
OB: The cooling of an ON-type is improved by air blast over the outside of the tank.
ON: The great majority of transformers are oil-immersed with natural cooling, the heat developed in the cores and coils is passed to the oil and hence to the tank walls.
OFB: For large transformers artificial cooling may be used. The OFB method comprises a forced circulation of the oil to a refrigerator, where it is cooled by air-blast.
OFN: The oil is circulated by pump to natural air coolers .
OW: An oil-immersed transformer of this type is cooled by the circulation of water in cooling-tubes situated at the top of the tank but below oil-level.
OFW: Similar to OFB, except that the refrigerator employs water instead of air blast for cooling the oil, which is circulated by pump from the transformer to the cooler
AN: Natural cooling by atmospheric circulation, without any special devices. The
transformer core and coils are open all round to the air. This method is confined to very small units at a few kV at low voltages.
AB: The cooling is improved by an air blast, directed by trunking and produced by a fan.
OB: The cooling of an ON-type is improved by air blast over the outside of the tank.
ON: The great majority of transformers are oil-immersed with natural cooling, the heat developed in the cores and coils is passed to the oil and hence to the tank walls.
OFB: For large transformers artificial cooling may be used. The OFB method comprises a forced circulation of the oil to a refrigerator, where it is cooled by air-blast.
OFN: The oil is circulated by pump to natural air coolers .
OW: An oil-immersed transformer of this type is cooled by the circulation of water in cooling-tubes situated at the top of the tank but below oil-level.
OFW: Similar to OFB, except that the refrigerator employs water instead of air blast for cooling the oil, which is circulated by pump from the transformer to the cooler
Power Transformer- Cooling System
Cooling System
The cooling of transformers differs from that of rotary machinery in that there is no inherent relative rotation to assist in the circulation of ventilating air. The losses are comparatively small, and the problem of cooling can in most cases be solved by reliance on natural self-ventilation.
The cooling of transformers differs from that of rotary machinery in that there is no inherent relative rotation to assist in the circulation of ventilating air. The losses are comparatively small, and the problem of cooling can in most cases be solved by reliance on natural self-ventilation.
Power Transformer-Sources of Contamination
External
External sources of contamination can generally be minimized by maintaining a sealed
system, but on some types of equipment this is not possible. Examples of external sources of contamination are moisture, oxygen, and solid debris introduced during maintenance of the equipment or during oil processing.
Internal
Internal sources of contamination can be controlled only to a limited extent because these sources of contamination are generally chemical reactions, they cannot be stopped, but their rates are determined by factors that are well understood and often controllable.
Internal sources of contamination
• Non-metallic particles such as cellulose particles from the paper and pressboard
• Metal particles from mechanical or electrical wear
• Moisture from the chemical degradation of cellulose(paper insulation and pressboard)
• Chemical degradation products of the oil that result from its oxidation (e.g.,acids,aldehydes, ketones)
External sources of contamination can generally be minimized by maintaining a sealed
system, but on some types of equipment this is not possible. Examples of external sources of contamination are moisture, oxygen, and solid debris introduced during maintenance of the equipment or during oil processing.
Internal
Internal sources of contamination can be controlled only to a limited extent because these sources of contamination are generally chemical reactions, they cannot be stopped, but their rates are determined by factors that are well understood and often controllable.
Internal sources of contamination
• Non-metallic particles such as cellulose particles from the paper and pressboard
• Metal particles from mechanical or electrical wear
• Moisture from the chemical degradation of cellulose(paper insulation and pressboard)
• Chemical degradation products of the oil that result from its oxidation (e.g.,acids,aldehydes, ketones)
Transformer-Insulating Media
Insulating Media
Insulating media in high voltage transformers consists of paper wrapped around the
conductors in the transformer coils plus mineral oil and pressboard to insulate the coils from ground. From the moment a transformer is placed in service, both the solid and liquid insulation begin a slow but irreversible process of degradation.
Solid Insulation — Paper
Paper and pressboard are composed primarily of cellulose, which is a naturally occurring polymer of plant origin.
Liquid Insulation — Oil
The insulating fluid that has the greatest use in electrical equipment is mineral oil. There are insulating materials that may be superior to mineral oil with respect to both dielectric and thermal properties; however none has achieved the requisite combination.
Insulating media in high voltage transformers consists of paper wrapped around the
conductors in the transformer coils plus mineral oil and pressboard to insulate the coils from ground. From the moment a transformer is placed in service, both the solid and liquid insulation begin a slow but irreversible process of degradation.
Solid Insulation — Paper
Paper and pressboard are composed primarily of cellulose, which is a naturally occurring polymer of plant origin.
Liquid Insulation — Oil
The insulating fluid that has the greatest use in electrical equipment is mineral oil. There are insulating materials that may be superior to mineral oil with respect to both dielectric and thermal properties; however none has achieved the requisite combination.
Transformer-Introduction
Introduction
A transformer is an energy transfer device. Electrical energy applied to the primary is converted to a magnetic field which in turn, induces a current in the secondary which carries energy to the load connected to the secondary. There are two main purposes for using transformers. The first is to convert the energy on the primary side to a different voltage level on the secondary side. The second purpose is to isolate the energy source from the destination. Transformers are generally divided into two main types. Power transformers are used to convert voltages and provide operating power for electrical devices, while signal transformers are used to transfer some type of useful information.
A transformer is an energy transfer device. Electrical energy applied to the primary is converted to a magnetic field which in turn, induces a current in the secondary which carries energy to the load connected to the secondary. There are two main purposes for using transformers. The first is to convert the energy on the primary side to a different voltage level on the secondary side. The second purpose is to isolate the energy source from the destination. Transformers are generally divided into two main types. Power transformers are used to convert voltages and provide operating power for electrical devices, while signal transformers are used to transfer some type of useful information.
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