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How are IEC-1010-1 and IEC-348 different? One of the main differences concerns spacing requirements. The IEC 1010-1 standard goes a step further than IEC-358 in the spacing requirements for a given maximum input-voltage rating. The standard refers to these spacings as "creepage" distance (along surfaces) and "clearance" distance (shortest distance through the air). Larger clearance distances enable the meter to withstand the higher overvoltage transients that may be found on the system being measured.
What is an overvoltage category, and what is the significance of Overvoltage Category III?
IEC-1010-1 specifies overvoltage category ratings, which relate to the probability of a voltage occurring (at some location) that is significantly higher than the voltage expected. For example, an unexpected voltage transient would be considered an overvoltage. Overvoltage categories range from I to IV, in increasing order of overvoltage level expected. They are not necessarily related to the nominal voltage level of the system.
Overvoltage IV is typically the...