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If there is a terminal block that has both a current and voltage rating, I am curious what are the risks of going above the voltage rating (but still staying under the current rating)? Would the likely scenario be that the isolation between adjacent terminal screws break down and cause arching?

I'm not planning on going outside the specs, but am just curious.

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  • \$\begingroup\$ Product safety and creepage related issues for dielectric breakdown prevail. \$\endgroup\$ Sep 27 '17 at 14:51
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These ratings are based on regulations regarding minimum creeping distances. These regulations are based on known values what is safe from experience. While it is possible to theoretically calculate distances for clean surfaces, it is not accurately possible for dirty surfaces. The regulations basically ensure that a device that is built and tested by an engineer in a clean state does still correctly work and not cause any damage or potentially harm any person once it has been out in the field for several years and accumulated dirt. If you look at the regulations, you will see that there are special (larger distance) requirements for environments that are especially dusty. Even more so if they are so dusty that a spark could cause an explosion (e.g. mills)

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    \$\begingroup\$ +1, but that last line is misleading. Creepage distances have nothing to do with preventing sparks. Explosive atmospheres require either complete enclosure of the circuit, or a design that is "intrinsically safe" -- no node stores enough energy to create a spark that could ignite dust/gas. \$\endgroup\$
    – Dave Tweed
    Sep 27 '17 at 14:51
  • \$\begingroup\$ True. But at least in Europe, there are special regulations for mills though, and they include a large isolation distance for anything that could potentially have the energy to cause a spark. \$\endgroup\$ Sep 27 '17 at 14:55

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