tahira Posted October 22, 2002 Report Share Posted October 22, 2002 how to calculate the SWG for earth wire , it also depend on load ?some body tell me the general rule i.e earth wire size half the cables used for equipment.plz tell me in detail Link to comment Share on other sites More sharing options...
BigMax Posted October 23, 2002 Report Share Posted October 23, 2002 Hello tahira, In general, the earth conductor should be large enough to 'safely' carry the prospective short circuit current. This really means that the earth conductor must be of sufficient cross sectional area to safely (ie without excessive temperature rise) carry the short circuit current until the branch protection device (ie circuit breaker/fuse) clears. In practice, how do you apply this information? Here in Australia, I would refer to Australian Standard AS3000, which lists common Active conductor sizes with minimum applicable Earth conductor sizes. In general, the size ratio varies by between 30-50% or so. Unfortunately there is no simpe fixed ratio. An alternative (and more complex, as per AS/NZS3008) approach is to calculate the size required based on prospective short circuit currents, expected fault duration and protective device clearing times. Most of this information is not readily available, therefore reference to AS3000 is easier (for me). My suggestion therefore would be to refer to your local standards. I hope this is helpfull. BigMax Link to comment Share on other sites More sharing options...
grobert Posted October 24, 2003 Report Share Posted October 24, 2003 In the USA we call it the "equipment grounding conductor". Its size ,is as stated above, is based on the OCP (over current protection) on the phase conductors serving said equipment. We follow table 250.122 from the NEC to size the ECG. Link to comment Share on other sites More sharing options...
Guest Posted February 6, 2004 Report Share Posted February 6, 2004 Originally posted by tahirahow to calculate the SWG for earth wire , it also depend on load ?some body tell me the general rule i.e earth wire size half the cables used for equipment.plz tell me in detail Link to comment Share on other sites More sharing options...
jhun Posted February 6, 2004 Report Share Posted February 6, 2004 Originally posted by tahirahow to calculate the SWG for earth wire , it also depend on load ?some body tell me the general rule i.e earth wire size half the cables used for equipment.plz tell me in detail 50% of your current load Link to comment Share on other sites More sharing options...
Guest Posted September 15, 2004 Report Share Posted September 15, 2004 the earth as to be half the conductor size over 16mm Link to comment Share on other sites More sharing options...
porky Posted January 21, 2007 Report Share Posted January 21, 2007 I disagree ....the earth wire should be greater or equal to the current carring conductor... It should offer less resistance to the flow of current or the fault current might take a different path ... Link to comment Share on other sites More sharing options...
AB2005 Posted January 22, 2007 Report Share Posted January 22, 2007 Hi Tahira; We are working at a new project and following JAAKKO POYRY standards. We also select the main earth conductor for machines the half size of power cable. If power cable is, for example, 120mm², then we select 70mm² earth conductor. "Don't assume any thing, always check/ask and clear yourself". Link to comment Share on other sites More sharing options...
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