In the USA, at the load end of a 2-meter #18 power cord, you can expect 100-200 
amps short-circuit current, but not more, due to the resistance of the power 
cord, the connectors, and the wiring to the breaker box.

If you assume that the source resistance is almost 1 ohm, the short-circuit 
current would be 120 amps, maybe down to 0.6 ohms and up to 200 amps (for a 
120-volt system).  The resistance of the 230-volt system will be more because 
the building wiring is smaller than North America, so the short-circuit current 
would be about the same.  


-----Original Message-----
From: Brian O'Connell [] 
Sent: Monday, November 20, 2017 10:26 AM
Subject: Re: [PSES] Regulatory requirements for MOVs placed line-to-ground on 
AC mains ports?

Mr. Woodgate,

Is there a recently published spec for a 'typical' 230V mains impedance for the 
EU? Have also noted that the source Zs in 61000-4-5 for the instrument seem 
rather high. So what is the basis for 1500A interrupt rating?

For U.S., even for an artificially low-Z electronic AC source, seldom see fault 
currents exceed 200A peak for 120V mains. Conversely, have noted that at over 
100A fault current, any fuse not rated for the 'high' interrupt value will 
probably explode.

So either our ratings are suspect, or perhaps the physics behind the standards 
are not complete?


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