Can anybody tell me what is the extra low, low, medium, high and extra high voltages?

Thanks in advance.

 

In the power distribution arena 13,800 volts is medium voltage and over 25,000 volts is high voltage but from a controls standpoint low voltage control is 24 volts and below. 24 volts is a good low voltage control voltage as it is generally higher than the noise that would affect the signals at the 5 volt level for example.

 

Voltage:
Extra-low voltage means any voltage up to and including 30V;
High voltage means any voltage above 750V;
Low voltage means any voltage from 31 to 750V inclusive;

Voltage of a circuit means the greatest root-mean-square (effective) voltage between any two conductors of the circuit concerned;

Voltage-to-ground means the voltage between any given live ungrounded part and any grounded part in the case of grounded circuits, or the greatest voltage existing in the circuit in the case of ungrounded circuits;

Tony Moscioni
Electrical Inspector
Electrical Safety Authority

 

ELV is 0-50 V (depends on country regulations - top can be 48 to 63 V)
LV is >50 to <1000
Don't know the exact limits for the top 3 "highs"

 

I think this question can only be answered if you state the country and field you are working in. In belgium, the utilities companies define low voltage as anything up to 1000V, medium voltage between 1 and 70kV and high voltage everything above 70kV.

 

The NEC defines medium voltage as those voltages between 600 and 6000. High voltage is above 6000. NEMA voltages are 460, 575, 2300, 4000 or 4600, 6600, 13.2KV.

 

There's a nice side bar on this topic on page 42 of the November 2002 Control Engineering issue.

-James Ingraham
Sage Automation, Inc.

 

What actually is ''medium voltage?''
What could be simpler than defining one range of medium voltages? Well, don't bet on that. Medium voltage (MV) is not uniformly defined. It varies by industry, application, standards-making bodies, technical associations, etc.

The National Electric Code defines MV as occupying the 601-6,000 V range, with 6,001 V and up designated as 'high voltage!' Institution of Electrical and Electronic Engineers' (IEEE) Std. 100 defines MV for system ratings as 'greater than 1,000 V and less than 100,000 V, followed by two more classes: high voltage and extra-high voltage. For power cables, yet other ranges are specified in IEEE Std. 100. In keeping with metric practice, 1 kV is considered the MV threshold in Europe. Some manufacturers designate medium voltage for wire and power cable products with a 5-69 kV range. And, of course, some servo motor folks regard their 460 V units as 'high voltage.'

For motors and variable-speed drives, a practical nominal MV range might run from 600 V up to 15 kV. Available products have a narrower range. In part, this is determined by existing 'common' voltages that exist globally. In the 60-Hz world, these are 2.3, 4.16, 6.6, and 13.2 kV, while 3.3, 6.0, and 10 kV are common to the 50-Hz metric world.

How these voltages are related to motor size is shown the main text tables. Still other voltages exist, depending on the local power grid or user preferences.

 

Ashok
I assume u are asking this with reference to some application. As such the question is not clear. Can you elaborate on the application ?

 

Responding to Ashok's Mon, Nov 18, 9:54 am, query:

In the USA the document covering "Standard Nominal System Voltages" Is ANSI (American National Standards Institute) C84.1-1989.

Three voltage classifications are defined:
o low =, < 1000 V.
o medium, > 1000 but =/< 100 kV.
o high, =/> than 100 kV but =/< than 230 kV.

There is no definition for "low-low voltage" nor "extra high." However, another Standard, C92.2-1987, covers systems above 230 kV.

If you need additional detail, contact me at: tal-2(AT)webtv.net

Regards,
Phil Corso, PE
(Boca Raton, FL)

 

Dear Mr. Manish,

My question was not related to any particular application. I thought there is a globally accepted voltage classification. After reading the replys, I understand there is no standard voltage classification.
Thank you every one for your valued reply.

Regards,
Ashok

 

Dear Ashok
as u might have noticed in the replies u recieved there is no standard 'standard' as such.
good luck on ur project.