What is the definition of low voltage, medium voltage, high voltage and extra high voltage?

Definitions vary somewhat but a general guide to the voltage categories are as follows:

Low Voltage (LV):              up to 1000V

Medium Voltage (MV):       between 1000 V and 45 kV

High Voltage (HV):            between 45 kV and 230 kV

Extra High Voltage (EHV):  from 230 kV and above


As a general rule, LV cables might be used in applications like fixed wiring; MV cables are critical power distribution (both for local grid power and for heavy-duty equipment); HV cables are aerial cables - overhead line for widescale power distribution - often installed on pylons (as are EHV cables).

Some electrical engineers will refer to High Voltage as anything over 1kV, completely skipping Medium Voltage, so if referencing cables do be clear on the voltage you are taking about!

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