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Alumina research for underground cables

2004

Dear all,

I am involve in a critical study which include electric data of Aluminum Oxide. The working condition, related to a section of HV Underground Cable sre the followings:

--------------- <-- Phase Conductor (HV: 120-230-400 kV)
xxxxxxxxxxxxxx <-- Insulated layer
--------------- <-- Aluminum Sheath (0 Voltage)

My question are:

1) Does water influence more than air the oxidation process and thickness ?
2) How the Aluminum Oxide could be electrically represented, i.e a capacitance, a capacitance with a conductance in parallel, etc..
3) Are there any reference values for such parameters ?
4) Does it exist a phenomenon like a breakdown if the voltage through the Oxidation layer exceeds a threshold value ?
5) Are there any reference data for that breakdown threshold ?

Any help will be appreciated.

Regards,

Andrea Mansoldo
power system analyst - Milan , Lombardia, Italy

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A quick web search finds: Dielectric Constant= 8-9; Breakdown Voltage= 30KV/mm for a 1mm sample; Loss Factor= 0.0008; Resistivity= 1x10^14 ohm-cm. Hope this helps.

Tom Gallant
- Long Beach, California, USA
2004