Voltage Levels – Confused? 

By on

I was having a conversation the other day about voltage levels.  While everyone was in agreement that low voltage was 1000 V and less, there was more confusion on the terms 'Medium Voltage' and 'High Voltage'.  

Our attempt to resolve this was to look at IEC60038 "Standard Voltages", 20002.  This didn't help in that the standard does not define the terms 'Low Voltage', 'Medium Voltage', etc.  However, what the standard does do is group voltages into bands and this is useful.

IEC 60038 Standard

The standard defines the following bands:

  • band 1 - A.C. systems 100 V to 1000 V
  • band 2 - A.C and D.C traction systems
  • band 3 - A.C. systems above 1 kV to 35 kV
  • band 4 - A.C. systems above 35 kV to 230 kV
  • band 5 - A.C. systems above 245 kV

A.C. systems 100 V to 1000 V

50 Hz three phase systems 230/400, 400/690 and 1000 V
60 Hz three phase systems 120/208, 240, 277/480, 480, 347/600 and 600 V
60 Hz Single phase three wire systems 120/240 V

Supply voltage range ±10 % at the supply terminals
Supply terminal to final equipment maximum 4% voltage drop

A.C and D.C traction systems

D.C. systems 600, 750, 1500, 3000 V
A.C. systems 6250, 15000, 25000 V

600 V and 6250 V are non preferred and should not be used if possible

A.C. systems above 1 kV to 35 kV

50 Hz systems - a) 3.3, 6.6, 11, 22, 33 kV
50 Hz systems - b) 3, 6, 10, 15, 20, 35 kV
60 Hz systems - c) 4.16, 12.47, 13.2, 13.8, 24.94, 34.5 kV

It is recommended that either (a) or (b) be used, not both

A.C. systems above 35 kV to 230 kV

Series I - 45, 66, 110, 132, 150, 220 kV
Series II - 69, 115, 138, 230 kV

Only one series should be used in each country

A.C. systems above 245 kV

Not being an expert on higher voltages the table was a little confusing to me, so I'm not going to try and summarise it.

Back to the problem

The standard didn't answer the original question, but it did provide useful background.    I would now be tempted to classify 'Low Voltage' as less than 1 kV, 'Medium Voltage' as above 1 kV to 35 kV and 'High Voltage' as 35 kV to 230 kV (with ultra high or extra high above 230 kV).   Feedback, comments or further insight into this is welcome.

Related Links

  Railway Electrification Voltages



Steven McFadyen's avatar Steven McFadyen

Steven has over twenty five years experience working on some of the largest construction projects. He has a deep technical understanding of electrical engineering and is keen to share this knowledge. About the author

myElectrical Engineering

comments powered by Disqus

  1. ManjoloPhiri's avatar ManjoloPhiri says:
    9/1/2011 2:11 PM

    The terms "High Voltage"," Medium Voltage", "Low voltage" are relative terms. Which means you are free to define them according to where you are working. Forexample where I work we have different voltages: 220V, 400V, 550V, 3.3 kV, 11 kV and 33 kV. So we have defined high voltage as anything above 650V, Medium voltage is above 240V up to 650V, low voltage is anything 240V and below. This is working for us.

    • Steven's avatar Steven says:
      9/1/2011 2:11 PM

      Electropedia has the following definition for medium voltage: medium voltage (abbreviation: MV) (not used in the UK in this sense, nor in Australia) any set of voltage levels lying between low and high voltage NOTE – The boundaries between medium and high voltage levels overlap and depend on local circumstances and history or common usage. Nevertheless the band 30 kV to 100 kV frequently contains the accepted boundary.

  2. Rhys Jones's avatar Rhys Jones says:
    9/26/2012 3:25 PM

    Steven

    I tend to take a steer from manufacturers; where it appears (as you have suggested) up to (an including) 1kV=LV; above 1kV upto 35/38kV=MV greater would be HV.

    If you look at Schneider, ABB, FKI, Eaton, Siemens et al, this seems to be the common levels for designating voltages against Low/Medium/High.

    For higher voltages, there seems to be some discussion as to whether HV or HT should be applied, but then I wouldn't feel qualified to work on anything above 33kV.


Comments are closed for this post:
  • have a question or need help, please use our Questions Section
  • spotted an error or have additional info that you think should be in this post, feel free to Contact Us



IEC 60287 Current Capacity of Cables - An Introduction

IEC 60287 "Calculation of the continuous current rating of cables (100% load factor)" is the International Standard which defines the procedures and equations...

Fault Calculations - Typical Equipment Parameters

A frequent problem in fault calculations is the obtaining of equipment parameters.  While it is always preferable to use the actual parameters of the equipment...

Meeting room of the future

The IET site has a video of a visit showing of a high tech meeting room developed at Napier University in Edinburgh. It a good demonstration of innovative...

Power Factor

Power factor is the ratio between the real power (P in kW) and apparent power (S in kVA) drawn by an electrical load. The reactive power (Q in kVAr)...

Maxwell's Equations - Introduction

Maxwell's Equations are a set of fundamental relationships, which govern how electric and magnetic fields interact. The equations explain how these fields...

Cable Sizing Software

When sizing cables nearly, everyone uses some form of software. This ranges from homespun spreadsheets to complex network analyses software. Each has its...

Aluminium Windings - Dry Type Transformers

The other day I was talking to a colleague who is a building services consultant.  Despite regularly specifying dry-type/cast resin transformers he was...

ANSI (IEEE) Protective Device Numbering

The widely used United Sates standard ANSI/IEEE C37.2 'Electrical Power System Device Function Numbers, Acronyms, and Contact Designations' deals with...

UPS Battery Sizing

Various techniques exist to enable the correct selection of batteries for UPS applications.  The procedure described below is one of the more common. ...

Frame Leakage Protection

While not as popular as it once was, frame leakage protection does still have some use in some circumstances.  In essence frame leakage is an earth fault...

Have some knowledge to share

If you have some expert knowledge or experience, why not consider sharing this with our community.  

By writing an electrical note, you will be educating our users and at the same time promoting your expertise within the engineering community.

To get started and understand our policy, you can read our How to Write an Electrical Note