Single Core High Voltage Power Cables 2

[RRaghunath]

Could any one please tell me the relationship between positive sequence and zero sequence resistance / reactance for single core HV power cables.
I am looking for this information in connection with distance protection setting calculations for the 33kV Cable distribution feeders.
I tried some cable manufacturers' websites such as Okonite but to no avail. It would be helpful if I can obtain typical values for different size cables.

Thanks in anticipation. Raghunath

 

[jghrist]

The sequence impedances of single core shielded cable are complicated to calculate and depend heavily on the size and type of shields, spacing of conductors, earth resistivity, etc. I have found the following references useful:

Westinghouse T&D Reference Book.
Siemens Power Cables and Their Application, Part 1.
Rating of Electrical Power Cables, George J. Anders, IEEE Press.

You should be able to get data for particular cables by contacting the manufacturer.

 

[RRaghunath]

Jghrist,

Thanks for the response. I was told by a colleague that the zero sequence impedance would be equal to the positive sequence one. Is he right? Raghunath

 

[jwerthman]

The positive and zero sequence impedances will not be the same. The current paths and flux linkages are quite different for a phase to phase or three phase fault versus a single-line-to-ground fault.

 

[jghrist]

I agree with jwerthman. For example, the positive-sequence impedance for 500 kcmil copper 15 kV cable with 5 mil copper tape shield with 1.5 inch flat spacing is 0.153 + j0.428 ohm/mile. The zero-sequence impedance (assuming 100 ohm-m soil resistivity) with fault current returning in both the shield and ground is 0.675 + j1.118 ohm/mile.

It would not be valid to use the ratio for this example on other cables or spacings.

 

[jbartos]

Suggestion: Visit

http://www.kerite.com/catalog/catalogfiles/impedance_data_power.htm

etc. for more info

 

[jbartos]

Suggestion: Visit

http://www.ece.utexas.edu/~grady/EE394_Spring99_Test_1.pdf

etc. for a little calculation

 

[RRaghunath]

Thanks every one. I am trying to get the info specific to the cable 3c*300Sqmm, 33kV, XLPE insulated from the manufacturer.

The responses from all of you have been quite inforamtive, thanks once again. Raghunath