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electrapap (Electrical) (OP)
6 Nov 05 15:25
What are the voltage ranges for medium and high voltage?
mpparent (Electrical)
6 Nov 05 15:30
I believe the standard is:

1000V to 100000V is medium.

over 100000V is High.

Mike
Helpful Member!  davidbeach (Electrical)
6 Nov 05 16:08
Low is <1000V
Medium is 1000V - 69kV
High is 69kV - 230kV
Extra High is >230kV
jraef (Electrical)
7 Nov 05 1:15
I found out that it depends upon your branch of Electrical Engineering. I once hired an intern who was still in school getting her BSEE. I had her doing some motor control diagrams and she came to me one day asking to what end I was putting all these series and parallel RC circuits together. I was puzled, but it came out that she thought a Normally Open contact symbol was a cap, and a Normally Closed symbol was a varistor. When I stopped laughing, she said "Oh well, I don't deal with this high voltage stuff anyway". To her, 120VAC was "high voltage". Turns out she was specializing in BSEE-CS, for Computer Science.

I have no idea if she ever graduated.

Eng-Tips: Help for your job, not for your homework  Read FAQ731-376

davidbeach (Electrical)
7 Nov 05 9:06
Actually, I need to correct mine: I left out UHV, so

Low is <1000V
Medium is 1000V - 69kV
High is 69kV - 230kV
Extra High is 230kV - 350kV
Ultra High is >350kV

(I think I have them about right, I don't have the IEEE definitions at hand.)
peebee (Electrical)
7 Nov 05 18:35
My 1986 IEEE Red Book agrees with mpparent's definitions above:

low < 1000v
1000<= medium < 100,000
high >= 100,000

The 1986 Red Book is obsolete but I'd be surprised if they changed these definitions.

Note that different NEC requirements generally kick in at about the 50 and 600-volt levels.
davidbeach (Electrical)
7 Nov 05 21:38
peebee, check a newer Red Book.  Mine is nearly 2000 miles away so I can't at the moment, but the IEEE does define rangers for Low, Medium, High, Extra High, and Ultra High.  I think that I am at least close, but may have some of the boundaries off a bit.

But under no case are these electronic "engineers" even close when they think that low voltage ends at 24V.

Once upon a time I was involved with the fit up of an environmental test chamber at a major chip manufacturer and the test engineer responsible for the chamber want to make sure that there wouldn't be any exposed high voltage that his circuit board assemblies might be exposed to.  I assured him there wouldn't; I bit my tongue, but wanted to tell him that there wasn't even any high voltage on site.  He probably wouldn't have understood anyway.
davidbeach (Electrical)
12 Nov 05 13:10
Well, according to the 1993 Red Book my first post was correct.  Now I'm not sure where I got the Ultra-High Voltage designation, but I know I've seen it somewhere.
cuky2000 (Electrical)
4 Dec 05 10:50
There is not single universal standard to classify the voltage level. Even though every voltage class has their particularity and historical development, the voltage level classification is entirely arbitrarily.

For instance, in the US there is not a consensus among, NEC, IEEE, utilities and consumers. For IEC low voltage is less than 1000 V and high voltage is above 1000 V.

Ultra High Voltage (UHV) is commonly accepted as the voltage level above 1000 kV.
Historical Note:
The term UHV was first used in 1967 in a research project founded by the Edison Electrical Institute and the Bonneville Power Administration evolved from the research initially sponsored by GE and the utility industry for the design and development of EHV transmission from 345 kV to 735 kV.  By the end of 1960’s, a 765 kV transmission line was in the design phase by the American Electric Power Service Corporation (AEP). Since 1975, the research on EHV and UHV has continued with significant progress. In 1980’s, transmission line of 1,100 kV was being considered. Right of way, EMF, economics and other concerns force to postpone any further implementation of UHV projects.


For additional information in this subject see the enclose information.

Zogzog (Electrical)
7 Mar 06 13:08
Davidbeach is right except UHV is >800kV, these are for equipment nominal system voltages

Scott Peterson
Training Manager
Power Plus Engineering
www.epowerplus.com

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