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Topic Title: 33kV Cable Operate at 11kV
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Created On: 22 March 2012 03:53 AM
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22 March 2012 03:53 AM
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pahmi

Posts: 2
Joined: 22 March 2012

Hi,

Guys, I need some help here. Let say if I have a 33kV cable installed in my network. If the network is converted from 33kV to 11kV, what is the maximum current carrying capacity of the 33kV cable operated at 11kV.

Below are the specs of the cable:

Type : Aerial Bundle Cable 3 x 150mm2
Voltage : 33kV
Capacity: 16.5MVA/288A
Max DC Resistance of Conductor : 0.33 Ohm/km
Max Capacitance : 0.171microFarad/km
Max charging current per cable : 1.0250 amps/km

Your help is greatly appreciated. TQ
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22 March 2012 12:33 PM
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alanjhodgart

Posts: 14
Joined: 11 September 2002

Capacity is the same as if operated at 33kV
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22 March 2012 02:16 PM
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folahanolaleye

Posts: 3
Joined: 14 February 2012

Let do it this way. lets use UPS technology or Stabilizer circuit unit. the parameters been set for UPS is to generate 240v, 12amps to 12amps. So your generation depends on the kind of transformer installed just as in stabilizer that can boost 190v to 240v,50Hz + 12A or via verso. Majorly u get the same current. it is on rear occasion you can boost the current like in metallurgy factory where transformer converting 33kv to 11kv, 100A with variable resistor to boost the current and voltage to 250A and 20kva BY using 5 control power boxes tall like a shelf connected in series . kindly see beyond this as it ideally technical for for me to analyze up to this moment
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22 March 2012 07:26 PM
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alancapon

Posts: 5523
Joined: 27 December 2005

Your cable will have the same current carrying capacity at 11kV, but the power you can carry will be a third of what you can achieve at 33kV - it will still be the 288A you quoted, but only 5.5MVA.

Regards,

Alan.
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23 March 2012 04:47 AM
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pahmi

Posts: 2
Joined: 22 March 2012

thanks guys..greatly appreciated all your response
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28 March 2012 12:13 PM
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broadgage

Posts: 1097
Joined: 07 August 2007

Yes, capacity in amps is the same at any voltage, for all practicle purposes.
At the lower voltage the dielectric losses in the cable insulation will be less, and less heat will be produced by these losses.
In theory this would permit of a VERY SLIGHTLY greater current at 11KV than at 33KV for the same conductor temperature.
In practice the effect is minute and the same current rating may be assumed.
I mention this to satisfy the pedant, rather than because it is of any practicle significance.

The capacity in KVA will of course be one third at the lower voltage.
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