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 High voltage. Low voltage.
We hear the term used often, but it would be good to have a definitive listing of what voltage
levels qualify for which levels. The table below lists some typical names and the corresponding
voltage levels. The video clip at the left appeared as a Cool Pic on RF Cafe a year or so
ago, and the one on the right was recently found. Both are awesome.
For human electrocution levels, please click
here.
| Safety Extra-Low1 |
≤42.2 Vac pk, ≤60 Vdc |
Considered "safe" for touching (although never recommended). Protected to "guarantee"
voltage will never rise above these levels, even under a fault condition. Double insulated. |
| Extra-Low1 |
≤42.2 Vac pk, ≤60 Vdc |
Non-touchable, but considered safe due to insulation from hazardous voltages. |
| Low2 |
≤1 kVac |
Considered hazardous. These level are found in common residential and commercial equipment
installations. |
| Medium3 |
>1 kVac to 100 kVac |
Very hazardous. Residential and small commercial transformers, both on poles and on the
ground. |
| High3 |
≥100 kVac to ≤230 kVac |
Very hazardous. Found in transmission grid systems including substations. |
| Extra-High4 |
>230 kVac to ≤800 kVac |
Extremely hazardous, even at a distance. Transmission systems between substations and
power generation. |
| Ultra-High4 |
>800 kVac to 2 MVac |
Extremely hazardous, even at a great distance. Transmission systems between substations
and power generation. |
References:1: IEC 60950-1 2: NEC-NFPA 70 low voltage = 600 V, ANSI/IEEE low voltage
= 1 kVac, EU's Low Voltage Directive = 50 V to 1 kVac & 75 to 1.5 kVdc 3: ANSI C84.1 &
IEEE 100 4: IEEE 1312 & IEEE 100
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