Voltage Levels – Confused?
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