Another question for Sparks please?


Postby Jeffmo » Wed Jun 20, 2007 8:22 pm

Hi Sparks , i have a ? which might crop up in my exam on monday and i just can't remember or grasp what formula or where i should gleam the information from . Wonder if you could help ? ...Heres an example :-
A 230 V 30 A RADIAL CIRCUIT IS PROTECTED BY A BS3036 DEVICE.IF THE VALUE OF PHASE EARTH LOOP IMPEDENCE FOR THE CIRCUIT IS 2.3OHMS,DISCONNECTION UNDER PHASE/EARTH FAULT CONDITION WILL OCCUR IN .....Thats the question format and i think the answer is 3 sec's but its how i get there that is the problem please advise as its starting to make me worry about the exam , which in theory shouldn't be a problem , its just one little thing makes me doubt myself , thats just me i want everything to be perfect and to do that i need to know what and why .Cheers Jeff
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Postby Jeffmo » Thu Jun 21, 2007 10:40 pm

[quote="Jeffmo"]Hi Sparks , i have a ? which might crop up in my exam on monday and i just can't remember or grasp what formula or where i should gleam the information from . Wonder if you could help ? ...Heres an example :-
A 230 V 30 A RADIAL CIRCUIT IS PROTECTED BY A BS3036 DEVICE.IF THE VALUE OF PHASE EARTH LOOP IMPEDENCE FOR THE CIRCUIT IS 2.3OHMS,DISCONNECTION UNDER PHASE/EARTH FAULT CONDITION WILL OCCUR IN .....Thats the question format and i think the answer is 3 sec's but its how i get there that is the problem please advise as its starting to make me worry about the exam , which in theory shouldn't be a problem , its just one little thing makes me doubt myself , thats just me i want everything to be perfect and to do that i need to know what and why .Cheers Jeff[/quote]
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Posts: 103
Joined: Mon Apr 09, 2007 9:22 am


Postby sparx » Thu Jun 21, 2007 10:50 pm

hi jeffmo, very late, books in van but i think tables 41b1/2 give max values for 0.4 or 5.0 sec disconnection times, these being only options if i understand ?
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