11kV vs 22kV electric distribution voltage

[asela115]

Hi,

what are the possible reasons for selecting 11kV underground distribution system vs 22kV underground distribution system for urban area.
I know about 22kV can carry twice the load compared to 22kV.

How about impacts of pricing, fault level, stepdown from 132 kv to 22/kv etc.

Thanks

 

[anorlunda]

That is far too broad a question to ask or answer on an online forum. Planning engineers use many tools to evaluate all the pros and cons of design choices. Your question could apply to any and every power distribution and transmission project.

If you don't have access to professional engineers in this field, I suggest that you search for textbooks.

 

[davenn]

That is far too broad a question to ask or answer on an online forum. Planning engineers use many tools to evaluate all the pros and cons of design choices. Your question could apply to any and every power distribution and transmission project.

If you don't have access to professional engineers in this field, I suggest that you search for textbooks.

agreed
and as a generalisation ... the obvious reason would be that it's much easier to insulate 11kV conductors than 22kV ones where they are pretty much in contact with each other ... lower voltage, lower chance of dielectric failure

Dave

 

[asela115]

thank you all for your valuable feedback (I should have shared following details beforehand)
this is a special project with following details. it has residential, hotels, government offices, cultural & educational centers etc. compacted in small area (a luxury compacted city build in small area).

• land area - 275 hectare
• population -300,000
• total expected maximum demand - 250 WM
• total demand- 500 MW

we are to justify a suitable distribution voltage for this special project. based on the feedback and details observed so far, i have summerised below details,
advantage of 22kv
1)Reduce by 50%

• space requirement for laying cables
• No of feeder bays

2)For double the capacity

• Increase only by around 10% to 15% cable cost
• Small price difference between 11kV and 22kV panel -design the panels for 22kV and fix 12kV equipment

3)Low energy loss in MV network
4)Low energy loss in HV equipment- 220kV can be directly stepped down to 22kV
5)No much difference in operation & maintenance of 11kV & 22kV cables & equipment
why 33kv is not best for this kind of project
1)33kV is a sub transmission voltage not a distribution voltage.
2)Cables and equipment very expensive.
3)RMUs are very expensive and very rare.
4)Cable systems are difficult to handle, operate & maintain.
5)Need more space for switch gear and cables
6)High fault level.
7)Cable capacitance would be high and need to have reactors at GSS

are there any technical matters we should consider beyond this. Especially I'm missing with accurate pricing details of cables and RMU/Switchgears (pricing comparison of 11kV, 22kV and 33kV).
Further in some posts I saw that having higher fault levels is good when considering starting of large motors etc. where neighboring consumers won't feel much (So, is 22kV better than 11kV)
Are there any examples where this kind of projects were carried out using 22kV (instead of 11kV)

 

[davenn]

OK well none of that was mentioned earlier

for all that you shouldn't be asking these sort of Q's on a forum
Instead hire qualified electrical engineers to assess the required specifications

Dave

 

[berkeman]

@asela115 -- we are contacting your employer to let them know that you are trying to design this project on your own using web forums, instead of paying a professional to do it for you. Good luck, this thread is closed.