Earth-fault proteciont 67n with etap 7.5

[Young.Engineer]

Hello to all!
I'm modelling a big (about 10km of cables) electrical network with ETAP 7.5 and I'm testing the earth-fault directional protections 67N.
There is one MV forniture, and the network is used in ring form.
My problem is this: if I simulate an earth-fault in the supply source (outside my network), ETAP doesn't calculate the CAPACITIVE current that flow between the network and the supply source (contribution of the network to the supply fault).
The neutre is compensated with Petersen coil, so a few amperes current has to flow, and this current could trip the first protection giving a black-out in all my network even though the fault is outside.
Anyone know how to simulate this capacitive current with ETAP??
Thanks!

[surgeArrester]

I am really sure about it. But, I think that there is no capacitive current since there is no capacitor. You see, you have to model the capacitor that somehow acts an natural capacitance between those objects. And I guess, maybe ETAP is not built with perhaps you could use PSCAD. But still you have to model the capacitances.

[Young.Engineer]

I agree with you, the problem is to simulate this capacitance...
Anyone know how simulate cable's capacitance to earth with ETAP?
Thanks!!

[surgeArrester]

I think you need to provide the value of susceptance in the impedance tab of the cables. It will treat the cables as pi, meaning 1/2 of the value in the ends are connected to earth. You can run load flow to that cable provided that there is no load connected to it. After the load flow, it will show some value and that is the current in that capacitance.

[yahiayahia]

thanqse

[surgeArrester]

Ur welcome


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[Pr0NiFt0]

Another way to achieve this is to model the cable with complete parameters, involving the geometry of it. Refer to the manual for the Cable Modelling process

[surgeArrester]

Hmmm... it is still the same..

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