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Gents if the proposed transmission line is at high altitude area (more than 2000m above sea level) with a span of 300km, 345kV..by simple high level analysis, what are the considerations to be made in design to minimise the line cost in terms of insulation voltage levels? thanks, Danilo

Thanks 7anoter4, if for instance Zdu is zero when fault occurred at the terminal of end of the cable, what sort of analysis should follow?

Gents,thanks for the replies. The assumed MVA Base is 100 MVA. Assuming the location of the fault at Cable D is at utility end and if the cable impedances of A,B & C are significant, does it make sense to include the cable impedances contribution into fault current? Davidbeach mentioned that...

I agree With the generator off; A fault adjacent to the utility bus will be limited by the utility immpedance. A fault on the generator bus will limited by the utility impedance and by the impedance of 4 cables in parallel. But when the generator is on, referring on the above diagram, I...

Thanks. i am trying to figure out if current divider principle can be applied to short circuit analysis. by just looking at the diagram ,the fault contribution from the generator appears to be divided among the 4 cables which includes the faulted cable D.Otherwise, the fault contribution from...

Thanks when CB is on and assuming the ff: cable impedances = 1 p.u/cable utility impedance = 0.5 p.u generator impdance = 1.5 p.u the fault current is 0.393 p.u. could you suggest how do you derive the generator contribution on the fault current? does part of the fault current from generator...

Gents, please see attached SLD..all loads are neglected. If CB is off and on, what is the equivalent circuit diagram? Cable is 5km long each. thanks, Danilo

Thanks again for the replies. Just to clarify that fault occured at one of the 33kV cable feeders terminated at 33kV bus (Utility) and the other end to 33kV generator bus where the CB is OFF. Immediately after the fault, can I neglect the impedance of the faulted cable? regards, Danilo

Gents thanks for your replies. I am thinking of neglecting the impedance of the cables during the fault condition at one of the cables when the generator CB is OFF and consider the cable impedance only when the generator is ON. I just dont know if my assumption is correct. what do you think...

Gents, Just want to get your opinion regarding the fault calculation on 33kV feeder line if the load are neglected and do not contribute into the fault and are fed by 4 x 33kV feeder cables 5km long and terminated to 33kV generator terminal bus at one end , should the impedance of cable...

Thanks Krisys..i will use it for the setting of distance relay..I agree with all of you to include the value of resistive component. I have a follow up question regarding angle displacement: Is it possible to have at the 132kv source an available MVA (positive phase sequence) with an angle...

Gents, Could you advise please if its normal to assume that parameters of positive phase sequence is equal to negative phase sequence at single line to ground fault? Is it possible to derive from positive and zero phase sequences reactive MVA ratings the source available MVA ? Grateful if...

Thanks..im thinking maybe by ignoring the R, the calculation is a bit conservative since the short circuit capacity of the line will increase. I just dont from the point of view of protection system if being conservative makes the system more reliable and secured..what do you think?

Thanks Gents for your replies. its 132kv line and the impedance is .9+j1.1 ohms..sorry for the error.. im doing a per unit method at the moment to initially compute the fault currents. is it recommended to ignore the R component of the line? regards, Danilo

Gents, I have a line impedance of 0.9+j0.1(positive phase sequence) on a 15km transmission line, can i ignore the 0.9 resistance in the calculation of fault current using per unit method? or is this still relevant given that length of transmission line? many thanks, Danilo

Thanks Marmite for your valuable input.I see your points clearly and i believe theres no language problem either..im just hypothetically figuring out what will happen if the air break switch is expossed to a fault level more than it can handlle..i got your point how it reacts to massive fault...

Gents thanks for your replies..to quote Marmite ' It shouldn't be damaged by a through fault if the current is within the short circuit rating.'..the ABS assembly im referring here is rated at short circuit fault of 25kA/1sec. My understanding of this is ,when the fault current exceeds 25kA...

Gents, Just a general inquiry that i hope would be worthy of discussion..is an Air Break Switch rated at 12/24kV considered as protection device for short circuit or it is just an isolator and meant to be damaged during fault condition? thanks, Danilo

Hi 7anoter4, Thanks for your replies..Could you advise please the specs (brand) of dry buzz stick or any other instruments they use to measure the sag? Many thanks

i think this is true if the L-G fault would occur at transformer tank..i dont know if this model applies also on L-G fault at distribution line, say, a fallen OH bare line conductor that touched the ground?