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It should be something about 70 micro Ohm for VCB with two breaks per pole and about 30-40 micro Ohm for one break VCB
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Why transmission voltages in India multiples of 11KV?
The original idea was to add 10% to the nominal voltage to allow for a voltage drop in transmission. The voltages used in power transmission follow that tradition so that common transmission voltages are 11, 33, 132 and 275 kV, although voltage drops of 10% would be against the regulations in most countries now.
Can Waste Transformer Oil be Regenerated?
Yes, Special Transformer Oil Regeneration System can recycle and regenerate the unqulified transformer oil.As is well known the Transformer plays an important role in the generation, transmission and distribution of electrical energy. Under load the transformer, dissipates heat and the insulating oil acts as a coolant as well as an effective dielectric. Due to the highly hygroscopic nature of the transformer oil, it absorbs moisture from windings, which leads to gradual deterioration of dielectric strength. Also there are some waste impurities, gas contents in the transformer oil which destroy the oil's quality.Transformer Oil Regeneration System is the most efficient and economical purification system.Special Transformer Oil Regeneration System is applied to filter various of unqualified insulation oils including aging transformer oil specially for the power which is above 110KV, mutual inductor oil, switch oil and so on. Also it can inject the insulating oil into the transformers on-line.Transformer Oil Regeneration System owns following Features:1. Duplex 3D stereo-evaporation, eliminating the liquid water quickly2. UK G technology by which the trace water that is show chain, such as dissolved water, can be removed effectively.3. Distinctive removing impurities system filtering through double FH trapezoidal network and absorbing by high polymer without the mechanical power4. Carbon fiber infrared heating system that can make the oil contains zero sum of ethyne after the treatment5. Especially applied to vacuum oiling and drying for power transmission equipments which are over 110KV6. The oil of any grades can be treated on line at the working site.7. Can be operated both on-load and off-load.8. Can be operated fully-automatically with PLC controller.9. this Oil purifier can be made in hermetical, canopy-covering, open and frame style.Transformer Oil Regeneration System Has Following Advantages:dewater, degas and removes the impurities more quickly, more completely, and makes the oils limiting voltage-withstand value much higher. As the bridge-type vacuum linking system that can purify and also can be an independent vacuum power supply, this machine can treat the electric insulation devices.Contact me for more information if you have any more questions via: kevinnchiang@gmail.com , or call me at 0086-135-2739-0908, or sent message to my MSN ID: new8628@hotmail.com .Additional Key Words:..... Transformer Oil Regeneration Systems, Turbine Oil Reclamation Systems, Lube Oil Purifier, Transformer Oil Purification Systems, Hydraulic Oil Filtration Machine, Compressor Oil Recycling Plant, insulation oil purifier, transformer oil purifcation systems, Oil Filtraton System, Oil Treatment Machine, Oil Cleaning System, Oil Recycling Machine, Oil Reclamation Machine, etc...kevinnchiang@gmail.com, new8628@hotmail.comCell: 0086-135-2739-0908
Can step down transformer be used as a step up transformer?
If the transformer has two separate windings, then, YES a step-down can be used as a step-up, and vice-versa.It is more correct to say you are reversing the high and low sides.By definition Primary is the "IN" side and Secondary is the "OUT" side.The Primary could be the high voltage side if it is a step-down,or it could be the low voltage side, if it is a step-up.Design ConsiderationsCare must be taken when reversing the operation of a step-down transformer to insure that it does not exceed the ratings of the transformer. For example, let's say we have a 12 VA step-down transformer that takes 120Vac in and is rated to provide 12V at 1 amp at the secondary. If we were to reverse it and apply 12Vac to the new primary (the old secondary), we would have 120Vac at the new secondary, but to keep within the original ratings it could only be loaded to 0.1A @ 120Vac.As long as you treat the output rating of the step-down transformer as the input rating as a step-up transformer, and don't try to draw current beyond what would normally have been applied to the high voltage primary, you should be fine. Potentially one could push up the voltage on such a transformer beyond what its stated application specified, while making sure not to exceed the power rating of the transformer and not exceeding the breakdown voltage of the transformer's insulation, for example driving the above transformer at 24V to get 0.05A @ 240Vac. It is important to realize though that the rated input voltage for a step-down transformer will likely not be a safe input voltage if you use it as a step-up transformer - for example, applying 120V to the above transformer with the windings reversed would generate 1.2KV!One important point to remember when reversing a three-phase transformer to a step-up is what kind of windings it has. Most three-phase transformers use a "delta" configuration on the primary side. This means that there are three "hot wires" and a ground, but not a neutral. (The white wire in a circuit). On the secondary side, transformers are usually wired up in a "Wye" (sometimes called a "star" configuration. Doing this allows the transformer to create a Neutral connection. If a step-down transformer is reversed to make it a step-up, the high (output) side will not have a Neutral connection. If one is not needed, say for a three-phase welding machine, this would not be a probem. However, if a Neutral IS needed ,say for lighting, reversing this transformer would not work. In this case, a listed step-up transformer will be needed. One final thing, if a step-down transformer is used as a step-up, a Neutral wire is not required to be connected to the input side.
Why was 120V chosen as the standard voltage of homes in the US and not some other voltage?
The reason that 120v service was chosen, was economic. Originally electricity was delivered to homes, and most businesses, for a single purpose and that was lighting. Can openers, TVs, washers, dryers, electrical factory machinery, etc. came later. At the time the most cost effective form of light bulb was a carbon filament bulb that operated best (optimally) at 100v to 110v. This, adjusted for transmission voltage drop, set most supply lines at 120v.Supplemental and Related Information:By the time cost effective, and higher voltage, metal filament bulbs were brought to the market, most of the cities in the USA were already running 120v supply lines. Europe was just starting such systems and opted for higher voltage supply lines.Higher voltages are used for long distance transmission and power distribution because more power can be transferred over the same size wire at a higher voltage (lower current). Power generation plants often use voltages in the hundreds of thousands, 115,000 to 165,000 of volts to move power over long distances. For lines of up to 20 miles long around a city, 2400 volts works well to reduce the voltage loss in the wires.In North America, the electrical power lines going to residential streets and roads are operated at a primary voltage of 7200 volts. This voltage (12500/1.73 = 7225) is one leg from a three phase 12500 volt primary line. On the secondary of the transformers it is center tapped to provide 120 volts from each 240-volt leg to the center point. The center point is electrically neutral. The actual measured voltage in your house receptacle circuits will normally be 110 to 120 volts. All appliances are rated for the minimum operating voltage (110-115). This is the cause of confusion about the actual level of the supply voltages.Different nominal voltage level and frequency standards are used in different countries. Europeans - and many other countries around the world - use 50 Hz (cycles per second) as the alternating frequency, not 60Hz as is used in North America and, again, many other countries around the world. The reason to use a higher voltage is that it is more economical because the current is less, so the wires can be smaller. On the other hand, the reason to use lower voltage in homes is safety: the lower the voltage, the safer it is.If you have 10 amps drawing on one leg of your 240/120 service, and 10 amps on the other leg, the I2R losses are one fourth what they would be if you had 20 amps on just the one leg.The Europeans use 415/240 (415/1.73 = 240), so their I2R losses are 1/16th of our 120 volt losses, with 20 amps drawing on just one leg.480 V center tapped (split phase) is used in the UK only rarely, typically in rural areas to supply an isolated small group of houses that can be fed off a single phase overhead spur. Most houses and small businesses are supplied with 240 V single phase taken from a 415 V three phase local system, fed from a transformer of up to 700 KVA connected to the 11 kV distribution system. The voltage is mostly 240 V but is nominally described as 230 V with a suitably wide tolerance, to comply with European standards.Originally, the service voltage was about 90 volts direct current, which was Edison's plan. Tesla proposed that the electrical grid be alternating current (AC) and competed with Edison for the first generating plant to be built in the State of New York at Niagara Falls. Edison proposed a DC system and Tesla an AC system. History tells us that Tesla won the competition, and because of that the industrial revolution was quickly accelerated. Had Edison won we would probably still be in the dark ages because of the inefficiency of transmitting DC current over long distances. While Edison was promoting the electrical light bulb around the country, almost every town required its own generating station because DC would lose so much in the transmission that it became unusable after only a couple of miles.Tesla also had invented the poly phase alternating current generators that provided for the ability to generate the voltages necessary for long distance transmission. Tesla kept the voltage about the same as what Edison started but raised it to the 110 volts alternating current (VAC) because of the higher related voltages of 220 VAC and 440 VAC, which were integral to the more efficient poly phase generators.The standard voltage available in most parts of the country (US) is now nominally 120 VAC volts +/- 10%, and can vary from 108 VAC to 132 VAC. It's usually around 117-118 VAC.Transmission distances, the actual power needed in a neighborhood, cost, efficiency and safety issues dictate service parameters. Common distribution voltages run up to 16,000 volts. 12,000 is very common but there is still a lot of activity adding on to legacy distribution grids at lower voltages. A 2400 volt primary is very low for a distribution transformer.In actuality power transmission is over many miles and the transmission voltage is more then 110kV. In fact interstate transmission is in the range of close to 500kV. At a substation it is reduced to 16kV for local area distribution. Transmission for the whole of the grid in North America is all tied together . Why? For economy and reliability. For example in the Summer some states do not use air conditioning but in Las Vegas, Nevada they do, so they actually buy the power from Canada in the summer because it is cost effective and reduces the need for more generation plants. Even then reserve spin power must be sustained for peak demands. Because power plants cannot produce near instant acceleration to meet new demands. In many cities and other peak demand areas, specialist peakers work to ensure that the the integrity of the grid is always maintained. 240 v is standard for the USA but only one phase is used and the transformer center tap is grounded, making it safer. Also, the main frequency of 60 Hz produced by power generation is not as stable as some people think. It varies throughout the day as loading changes but the controllers must legally ensure that it averages 60Hz over a complete day so that electric clocks using synchronous motors remain accurate.
How do I convert short circuit current to fault level. I have a 110kV grid which has a maximum short ccircuit current of 30kA?
It is very simple. Use the following equation: Smax=sqrt(3)*V(line-line)*Isc(max) for your case: Smax=5715.76 MVA
What is the voltage coming out of a station?
Depends on the sub station. It could be 11KV, 33KV, 66KV,110KV, 220KV, 400 KV etc
Existing location of gas insulated substations in India?
There are 230kv and 110kv GIS substations in chennai functioning from 1998 ,commssioned by Tamilnadu electricity board.
Why has line voltage increased since 1960?
Line voltage has increased because more power can be transported at higher voltages with less I^2*R losses (loss due to the line resistance). This is why systems originally designed for 110kV may have had minor upgrades to 115kV, and are often run near 1.04% of this (120-121kV) most of the time. This allows more power to be transported with minimal investment.
Why are some transformers oil filled?
Transformer oil, or insulating oil, is usually a highly-refined mineral oil that is stable at high temperatures and has excellent electrical insulating properties. It is used in oil-filled transformers, some types of high voltage capacitors, fluorescent lamp ballasts, and some types of high voltage switches and circuit breakers. Its functions are to insulate, suppress corona and arcing, and to serve as a coolant.After Transformer oil is used for a long-period, the oil will turn to dark liquid. The Transformer plays an important role in the generation, transmission and distribution of electrical energy. Under load the transformer, dissipates heat and the insulating oil acts as a coolant as well as an effective dielectric.Due to the highly hygroscopic nature of the transformer oil, it absorbs moisture from windings, which leads to gradual deterioration of dielectric strength. Also there are some waste impurities, gas contents in the transformer oil which destroy the oil's quality.Hi-tech Vacuum Transformer Oil Purification Systems is the most efficient and economical purification system.Hi-tech Vacuum Transformer Oil Purification Systems is applied to filter various of unqualified insulation oils including aging transformer oil specially for the power which is above 110KV, mutual inductor oil, switch oil and so on. Also it can inject the insulating oil into the transformers on-line.Hi-tech Vacuum Transformer Oil Purification Systems has the great abilities in removing impurities, particles, water content, gas content, acid, etc... making the waste transformer oil to be regenerated to new oil's quality for reuse.for more information, welcome to visit http://bestoilpurifier.bossgoo.com , or email us kevinnchiang@gmail.comAll the polution problems caused by waste oil will be solved by Hi-tech Vacuum Transformer Oil Purification Systems.
Why transmission voltages in India multiples of 11KV?
The original idea was to add 10% to the nominal voltage to allow for a voltage drop in transmission. The voltages used in power transmission follow that tradition so that common transmission voltages are 11, 33, 132 and 275 kV, although voltage drops of 10% would be against the regulations in most countries now.
What voltage does New Zealand use?
New Zealand uses 230 V @ 50 Hz, the same as the UK and Australia. Wall power outlets are the same as Australia - two flat live and neutral blades in an inverted-V shape, with a single vertical flat earth pin below New Zealand's mains supply is incompatible with appliances designed for the US and Canada (120 V @ 60 Hz) - so do not attempt to put a US appliance in a NZ socket by bending the pins. High voltage lines are usually at 230/400 V, 6.6kV, 11kV, 22kV (local distribution), 33kV, 50kV, 66kV (sub-transmission), 110kV, 220kV (transmission) and +/-350kV HVDC (the inter-island link connecting the North and South Islands across Cook Strait)
Can Waste Transformer Oil be Regenerated?
Yes, Special Transformer Oil Regeneration System can recycle and regenerate the unqulified transformer oil.As is well known the Transformer plays an important role in the generation, transmission and distribution of electrical energy. Under load the transformer, dissipates heat and the insulating oil acts as a coolant as well as an effective dielectric. Due to the highly hygroscopic nature of the transformer oil, it absorbs moisture from windings, which leads to gradual deterioration of dielectric strength. Also there are some waste impurities, gas contents in the transformer oil which destroy the oil's quality.Transformer Oil Regeneration System is the most efficient and economical purification system.Special Transformer Oil Regeneration System is applied to filter various of unqualified insulation oils including aging transformer oil specially for the power which is above 110KV, mutual inductor oil, switch oil and so on. Also it can inject the insulating oil into the transformers on-line.Transformer Oil Regeneration System owns following Features:1. Duplex 3D stereo-evaporation, eliminating the liquid water quickly2. UK G technology by which the trace water that is show chain, such as dissolved water, can be removed effectively.3. Distinctive removing impurities system filtering through double FH trapezoidal network and absorbing by high polymer without the mechanical power4. Carbon fiber infrared heating system that can make the oil contains zero sum of ethyne after the treatment5. Especially applied to vacuum oiling and drying for power transmission equipments which are over 110KV6. The oil of any grades can be treated on line at the working site.7. Can be operated both on-load and off-load.8. Can be operated fully-automatically with PLC controller.9. this Oil purifier can be made in hermetical, canopy-covering, open and frame style.Transformer Oil Regeneration System Has Following Advantages:dewater, degas and removes the impurities more quickly, more completely, and makes the oils limiting voltage-withstand value much higher. As the bridge-type vacuum linking system that can purify and also can be an independent vacuum power supply, this machine can treat the electric insulation devices.Contact me for more information if you have any more questions via: kevinnchiang@gmail.com , or call me at 0086-135-2739-0908, or sent message to my MSN ID: new8628@hotmail.com .Additional Key Words:..... Transformer Oil Regeneration Systems, Turbine Oil Reclamation Systems, Lube Oil Purifier, Transformer Oil Purification Systems, Hydraulic Oil Filtration Machine, Compressor Oil Recycling Plant, insulation oil purifier, transformer oil purifcation systems, Oil Filtraton System, Oil Treatment Machine, Oil Cleaning System, Oil Recycling Machine, Oil Reclamation Machine, etc...kevinnchiang@gmail.com, new8628@hotmail.comCell: 0086-135-2739-0908
Can step down transformer be used as a step up transformer?
If the transformer has two separate windings, then, YES a step-down can be used as a step-up, and vice-versa.It is more correct to say you are reversing the high and low sides.By definition Primary is the "IN" side and Secondary is the "OUT" side.The Primary could be the high voltage side if it is a step-down,or it could be the low voltage side, if it is a step-up.Design ConsiderationsCare must be taken when reversing the operation of a step-down transformer to insure that it does not exceed the ratings of the transformer. For example, let's say we have a 12 VA step-down transformer that takes 120Vac in and is rated to provide 12V at 1 amp at the secondary. If we were to reverse it and apply 12Vac to the new primary (the old secondary), we would have 120Vac at the new secondary, but to keep within the original ratings it could only be loaded to 0.1A @ 120Vac.As long as you treat the output rating of the step-down transformer as the input rating as a step-up transformer, and don't try to draw current beyond what would normally have been applied to the high voltage primary, you should be fine. Potentially one could push up the voltage on such a transformer beyond what its stated application specified, while making sure not to exceed the power rating of the transformer and not exceeding the breakdown voltage of the transformer's insulation, for example driving the above transformer at 24V to get 0.05A @ 240Vac. It is important to realize though that the rated input voltage for a step-down transformer will likely not be a safe input voltage if you use it as a step-up transformer - for example, applying 120V to the above transformer with the windings reversed would generate 1.2KV!One important point to remember when reversing a three-phase transformer to a step-up is what kind of windings it has. Most three-phase transformers use a "delta" configuration on the primary side. This means that there are three "hot wires" and a ground, but not a neutral. (The white wire in a circuit). On the secondary side, transformers are usually wired up in a "Wye" (sometimes called a "star" configuration. Doing this allows the transformer to create a Neutral connection. If a step-down transformer is reversed to make it a step-up, the high (output) side will not have a Neutral connection. If one is not needed, say for a three-phase welding machine, this would not be a probem. However, if a Neutral IS needed ,say for lighting, reversing this transformer would not work. In this case, a listed step-up transformer will be needed. One final thing, if a step-down transformer is used as a step-up, a Neutral wire is not required to be connected to the input side.
Why was 120V chosen as the standard voltage of homes in the US and not some other?
The reason that 120v service was chosen, was economic. Originally electricity was delivered to homes, and most businesses, for a single purpose and that was lighting. Can openers, TVs, washers, dryers, electrical factory machinery, etc. came later. At the time the most cost effective form of light bulb was a carbon filament bulb that operated best (optimally) at 100v to 110v. This, adjusted for transmission voltage drop, set most supply lines at 120v.Supplemental and Related Information:By the time cost effective, and higher voltage, metal filament bulbs were brought to the market, most of the cities in the USA were already running 120v supply lines. Europe was just starting such systems and opted for higher voltage supply lines.Higher voltages are used for long distance transmission and power distribution because more power can be transferred over the same size wire at a higher voltage (lower current). Power generation plants often use voltages in the hundreds of thousands, 115,000 to 165,000 of volts to move power over long distances. For lines of up to 20 miles long around a city, 2400 volts works well to reduce the voltage loss in the wires.In North America, the electrical power lines going to residential streets and roads are operated at a primary voltage of 7200 volts. This voltage (12500/1.73 = 7225) is one leg from a three phase 12500 volt primary line. On the secondary of the Transformers it is center tapped to provide 120 volts from each 240-volt leg to the center point. The center point is electrically neutral. The actual measured voltage in your house receptacle circuits will normally be 110 to 120 volts. All appliances are rated for the minimum operating voltage (110-115). This is the cause of confusion about the actual level of the supply voltages.Different nominal voltage level and frequency standards are used in different countries. Europeans - and many other countries around the world - use 50 Hz (cycles per second) as the alternating frequency, not 60Hz as is used in North America and, again, many other countries around the world. The reason to use a higher voltage is that it is more economical because the current is less, so the wires can be smaller. On the other hand, the reason to use lower voltage in homes is safety: the lower the voltage, the safer it is.If you have 10 amps drawing on one leg of your 240/120 service, and 10 amps on the other leg, the I2R losses are one fourth what they would be if you had 20 amps on just the one leg.The Europeans use 415/240 (415/1.73 = 240), so their I2R losses are 1/16th of our 120 volt losses, with 20 amps drawing on just one leg.480 V center tapped (split phase) is used in the UK only rarely, typically in rural areas to supply an isolated small group of houses that can be fed off a single phase overhead spur. Most houses and small businesses are supplied with 240 V single phase taken from a 415 V three phase local system, fed from a transformer of up to 700 KVA connected to the 11 kV distribution system. The voltage is mostly 240 V but is nominally described as 230 V with a suitably wide tolerance, to comply with European standards.Originally, the service voltage was about 90 volts direct current, which was Edison's plan. Tesla proposed that the electrical grid be alternating current (AC) and competed with Edison for the first generating plant to be built in the State of New York at Niagara falls. Edison proposed a DC system and Tesla an AC system. History tells us that Tesla won the competition, and because of that the industrial revolution was quickly accelerated. Had Edison won we would probably still be in the dark ages because of the inefficiency of transmitting DC current over long distances. While Edison was promoting the electrical light bulb around the country, almost every town required its own generating station because DC would lose so much in the transmission that it became unusable after only a couple of miles.Tesla also had invented the poly phase alternating current generators that provided for the ability to generate the voltages necessary for long distance transmission. Tesla kept the voltage about the same as what Edison started but raised it to the 110 volts alternating current (VAC) because of the higher related voltages of 220 VAC and 440 VAC, which were integral to the more efficient poly phase generators.The standard voltage available in most parts of the country (US) is now nominally 120 VAC volts +/- 10%, and can vary from 108 VAC to 132 VAC. It's usually around 117-118 VAC.Transmission distances, the actual power needed in a neighborhood, cost, efficiency and safety issues dictate service parameters. Common distribution voltages run up to 16,000 volts. 12,000 is very common but there is still a lot of activity adding on to legacy distribution grids at lower voltages. A 2400 volt primary is very low for a distribution transformer.In actuality power transmission is over many miles and the transmission voltage is more then 110kV. In fact interstate transmission is in the range of close to 500kV. At a substation it is reduced to 16kV for local area distribution. Transmission for the whole of the grid in North America is all tied together . Why? For economy and reliability. For example in the Summer some states do not use air conditioning but in Las Vegas, Nevada they do, so they actually buy the power from Canada in the summer because it is cost effective and reduces the need for more generation plants. Even then reserve spin power must be sustained for peak demands. Because power plants cannot produce near instant acceleration to meet new demands. In many cities and other peak demand areas, specialist peakers work to ensure that the the integrity of the grid is always maintained. 240 v is standard for the USA but only one phase is used and the transformer center tap is grounded, making it safer. Also, the main frequency of 60 Hz produced by power generation is not as stable as some people think. It varies throughout the day as loading changes but the controllers must legally ensure that it averages 60Hz over a complete day so that electric clocks using synchronous motors remain accurate.
Why was 120V chosen as the standard voltage of homes in the US and not some other voltage?
The reason that 120v service was chosen, was economic. Originally electricity was delivered to homes, and most businesses, for a single purpose and that was lighting. Can openers, TVs, washers, dryers, electrical factory machinery, etc. came later. At the time the most cost effective form of light bulb was a carbon filament bulb that operated best (optimally) at 100v to 110v. This, adjusted for transmission voltage drop, set most supply lines at 120v.Supplemental and Related Information:By the time cost effective, and higher voltage, metal filament bulbs were brought to the market, most of the cities in the USA were already running 120v supply lines. Europe was just starting such systems and opted for higher voltage supply lines.Higher voltages are used for long distance transmission and power distribution because more power can be transferred over the same size wire at a higher voltage (lower current). Power generation plants often use voltages in the hundreds of thousands, 115,000 to 165,000 of volts to move power over long distances. For lines of up to 20 miles long around a city, 2400 volts works well to reduce the voltage loss in the wires.In North America, the electrical power lines going to residential streets and roads are operated at a primary voltage of 7200 volts. This voltage (12500/1.73 = 7225) is one leg from a three phase 12500 volt primary line. On the secondary of the transformers it is center tapped to provide 120 volts from each 240-volt leg to the center point. The center point is electrically neutral. The actual measured voltage in your house receptacle circuits will normally be 110 to 120 volts. All appliances are rated for the minimum operating voltage (110-115). This is the cause of confusion about the actual level of the supply voltages.Different nominal voltage level and frequency standards are used in different countries. Europeans - and many other countries around the world - use 50 Hz (cycles per second) as the alternating frequency, not 60Hz as is used in North America and, again, many other countries around the world. The reason to use a higher voltage is that it is more economical because the current is less, so the wires can be smaller. On the other hand, the reason to use lower voltage in homes is safety: the lower the voltage, the safer it is.If you have 10 amps drawing on one leg of your 240/120 service, and 10 amps on the other leg, the I2R losses are one fourth what they would be if you had 20 amps on just the one leg.The Europeans use 415/240 (415/1.73 = 240), so their I2R losses are 1/16th of our 120 volt losses, with 20 amps drawing on just one leg.480 V center tapped (split phase) is used in the UK only rarely, typically in rural areas to supply an isolated small group of houses that can be fed off a single phase overhead spur. Most houses and small businesses are supplied with 240 V single phase taken from a 415 V three phase local system, fed from a transformer of up to 700 KVA connected to the 11 kV distribution system. The voltage is mostly 240 V but is nominally described as 230 V with a suitably wide tolerance, to comply with European standards.Originally, the service voltage was about 90 volts direct current, which was Edison's plan. Tesla proposed that the electrical grid be alternating current (AC) and competed with Edison for the first generating plant to be built in the State of New York at Niagara Falls. Edison proposed a DC system and Tesla an AC system. History tells us that Tesla won the competition, and because of that the industrial revolution was quickly accelerated. Had Edison won we would probably still be in the dark ages because of the inefficiency of transmitting DC current over long distances. While Edison was promoting the electrical light bulb around the country, almost every town required its own generating station because DC would lose so much in the transmission that it became unusable after only a couple of miles.Tesla also had invented the poly phase alternating current generators that provided for the ability to generate the voltages necessary for long distance transmission. Tesla kept the voltage about the same as what Edison started but raised it to the 110 volts alternating current (VAC) because of the higher related voltages of 220 VAC and 440 VAC, which were integral to the more efficient poly phase generators.The standard voltage available in most parts of the country (US) is now nominally 120 VAC volts +/- 10%, and can vary from 108 VAC to 132 VAC. It's usually around 117-118 VAC.Transmission distances, the actual power needed in a neighborhood, cost, efficiency and safety issues dictate service parameters. Common distribution voltages run up to 16,000 volts. 12,000 is very common but there is still a lot of activity adding on to legacy distribution grids at lower voltages. A 2400 volt primary is very low for a distribution transformer.In actuality power transmission is over many miles and the transmission voltage is more then 110kV. In fact interstate transmission is in the range of close to 500kV. At a substation it is reduced to 16kV for local area distribution. Transmission for the whole of the grid in North America is all tied together . Why? For economy and reliability. For example in the Summer some states do not use air conditioning but in Las Vegas, Nevada they do, so they actually buy the power from Canada in the summer because it is cost effective and reduces the need for more generation plants. Even then reserve spin power must be sustained for peak demands. Because power plants cannot produce near instant acceleration to meet new demands. In many cities and other peak demand areas, specialist peakers work to ensure that the the integrity of the grid is always maintained. 240 v is standard for the USA but only one phase is used and the transformer center tap is grounded, making it safer. Also, the main frequency of 60 Hz produced by power generation is not as stable as some people think. It varies throughout the day as loading changes but the controllers must legally ensure that it averages 60Hz over a complete day so that electric clocks using synchronous motors remain accurate.
