Single Phase Voltage from 3-Phase Line: Explained

In summary, the line voltage of one of the single phase lines in a 3 phase line with a 25kV line-to-line voltage will be 14.4 kV. This is because single phase lines require a neutral side to create a loop, and the voltage differential between the line and the neutral is +/- 14.4 kV. The single phase transformers convert the 25kV line voltage to the user voltage with the ground reference applied at the secondary neutral. This is typically done for urban and suburban overhead and underground distribution in the USA, while Europe uses 3-phase secondary distribution. The neutral designation in the USA is MGN, or multiple grounded neutral, and is used as the final distribution to the LNL
  • #1
louie
10
0
If I'm considering a 3 phase line (25kV line-to-line voltage) that comes to a point and splits into single phase lines, what is the line voltage of one of the single phase lines ?

Does it remain 25 kV or is it 14.4 kV because you're only dealing with 1 phase and a neutral now ?

Any explanation would be great

Louie
 
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  • #2
Normally, they do not distribute L-N = Vl/sqrt(3)=14.4kV, only L-L =25kV. The phases can split AB, BC, CA. The single phase transformers convert 25K--> user voltage with the ground reference applied at the secondary neutral.
 
  • #3
A single phase line by definition is a circuit with only one phase. So you need a neutral side to create a loop. The voltage differential between the line and the neutral is, of course, +/- 14.4 kV and not 25 kV.

If you use both line (AB, AC, or BC) ... I don't think that a single phase line. It may be within the category of two phase line :-)

aaNg
 
  • #4
For distribution purpose only line voltages preferred so neutral is not used. And 25KV will not be splitted into single phase directly it will be step downed and than you will get a sinle phase line. sinle phase line voltage depends on the transformer rating.
rgds
Mahadev
 
  • #5
Actually, The main method of urban and suburban over head and URD is done single phase with line-neutra *in the usa*, europe is 3-phase secondary distribution 3-phases+ 2*line voltage = 8* the secondary line distance over the US, the neutral designation is MGN, or multiple grounded neutral, It is a lower wire of the four, or sometimes used as a top wire overhead shield in lightning prone areas. the L-N is used as the final distribution to the LNL +120 N -120 final use in typical residential apps.
 

1. What is single phase voltage from a 3-phase line?

Single phase voltage from a 3-phase line refers to the voltage that is obtained from one phase of a 3-phase power supply. In a 3-phase system, there are three separate voltage waveforms that are 120 degrees out of phase with each other. By only using one of these phases, a single phase voltage can be obtained.

2. How is single phase voltage obtained from a 3-phase line?

To obtain single phase voltage from a 3-phase line, a single phase transformer is used. The transformer will only utilize one of the three phases and will step down the voltage to the desired level for single phase use. This results in a single phase voltage that is 120 degrees out of phase with the other two phases.

3. What is the difference between single phase and 3-phase voltage?

The main difference between single phase and 3-phase voltage is the number of voltage waveforms present. Single phase voltage has one voltage waveform, while 3-phase voltage has three voltage waveforms. Additionally, 3-phase voltage is typically used for larger industrial or commercial applications, while single phase voltage is more commonly used for residential purposes.

4. What are the advantages of using single phase voltage from a 3-phase line?

Using single phase voltage from a 3-phase line can provide a more efficient and cost-effective solution for smaller power needs. It reduces the need for additional equipment and wiring, and it can be used for a variety of household and small commercial applications. Additionally, single phase voltage is more readily available in most areas compared to 3-phase voltage.

5. Are there any limitations to using single phase voltage from a 3-phase line?

Yes, there are some limitations to using single phase voltage from a 3-phase line. Single phase voltage has lower power capacity compared to 3-phase voltage, so it may not be suitable for larger industrial or commercial applications. Additionally, it may not provide as stable of a power supply as 3-phase voltage, which can be an issue for more sensitive equipment.

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