MINIMUM FAULT CURRENT CALCULATION
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ron
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Re: MINIMUM FAULT CURRENT CALCULATION
30 cycles is a long time (in the world of electrical faults).
Could you tell us why this may be important? Most equipment gets evaluated based on max. fault current calculations.
Does the equipment you are evaluating have only a 30 cycle rating?
30 cycles is a long time (in the world of electrical faults).
Could you tell us why this may be important? Most equipment gets evaluated based on max. fault current calculations.
Does the equipment you are evaluating have only a 30 cycle rating?
Re: MINIMUM FAULT CURRENT CALCULATION
hello Ron, thank you for your response and sorry for the delay in reply . no, 30 cycle i am stating because that's what i found in IEEE book for minimum current . this may be required for protection coordination. frankly , i have never used it but client wants this calculation.
proj
hello Ron, thank you for your response and sorry for the delay in reply . no, 30 cycle i am stating because that's what i found in IEEE book for minimum current . this may be required for protection coordination. frankly , i have never used it but client wants this calculation.
proj
ron
Senior Member
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- New York, 40.7514,-73.9925
Re: MINIMUM FAULT CURRENT CALCULATION
You will perform a regular fault calculation. 30 cycle rated equipment is rated to handle the rated value for 30 cycles, where the worst case will be instantaneous.
You will perform a regular fault calculation. 30 cycle rated equipment is rated to handle the rated value for 30 cycles, where the worst case will be instantaneous.
Re: MINIMUM FAULT CURRENT CALCULATION
no,ron.i think 30 cycle fault current means after 30 cycle, fault current wave peak comes down to what minimum value. and to check whether that is enough to operate certain time delayed relay. in my opinion , it is not the question of time but the value of fault current. don"t think it"s rude of me to reply so late. my office has stopped internet facility at every desk, so i can access sites only at home. and i am so busy with office work there"s hardly anyrtime to open home computer.
thanks .
no,ron.i think 30 cycle fault current means after 30 cycle, fault current wave peak comes down to what minimum value. and to check whether that is enough to operate certain time delayed relay. in my opinion , it is not the question of time but the value of fault current. don"t think it"s rude of me to reply so late. my office has stopped internet facility at every desk, so i can access sites only at home. and i am so busy with office work there"s hardly anyrtime to open home computer.
thanks .
Re: MINIMUM FAULT CURRENT CALCULATION
proj
When you have a fault occur you have asymmetrical
fault and symetrical fault currents. The asymmetrical fault is composed of two components.
One is the AC symetrical plus a DC component that is dependent on the X/R ratio. The X/R is the reactance and resistance of the system from the source to the fault. This DC current is at its peak during the first few cycles of the fault and decays expodentially over a period of time. After a few cycles you are left with just the symetrical fault current which is what you are after.
[ June 15, 2004, 07:33 PM: Message edited by: bob ]
proj
When you have a fault occur you have asymmetrical
fault and symetrical fault currents. The asymmetrical fault is composed of two components.
One is the AC symetrical plus a DC component that is dependent on the X/R ratio. The X/R is the reactance and resistance of the system from the source to the fault. This DC current is at its peak during the first few cycles of the fault and decays expodentially over a period of time. After a few cycles you are left with just the symetrical fault current which is what you are after.
[ June 15, 2004, 07:33 PM: Message edited by: bob ]
Re: MINIMUM FAULT CURRENT CALCULATION
no, bob. i have already calculated max. symmetrical and max asymmetrical current. but after 30 cycles symmetrical current does not have the same value as it was at the start of the fault. please refer IEEE in this respect. my question was how to get to that value. i found in one calculation done by ABB,they have calculated taking one 'c' factor. but how they derived that c value is not clear to me.
no, bob. i have already calculated max. symmetrical and max asymmetrical current. but after 30 cycles symmetrical current does not have the same value as it was at the start of the fault. please refer IEEE in this respect. my question was how to get to that value. i found in one calculation done by ABB,they have calculated taking one 'c' factor. but how they derived that c value is not clear to me.
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