I have a 185mm Al 11kV pair of cabl

[fb599]

I have a 185mm Al 11kV pair of cables rated at around 330A each. Both are feeding an area with max loading 140A. However, two 3.3MVA 11kV capacitors (175A each)have been added to this dist. area and are used from time to time. What will the cable max rating be if this new load is so capacitivly reactive. I can't simply add the currents can I ? Any good rules of thumb here ?

fb599

 

[electrifire]

You have to add the currents vectorally taking into account the current at 0 degrees, 90 degrees lagging and 90 degrees leading.

Why so much capitance on the low loads? This amount of capitance with out off setting lagging power factor may cause voltage increase that may cause system overvoltage.

 

[jbartos]

Suggestion: Considering sizes, amount of equipment and load, it may be better to have a good calculation/analysis performed, e.g. by software. It could save you some money down the road.

 

[fb599]

Thanks for the replies. It is part of a bigger picture for a cable link compensation arrangement. Thanks all the same. I'll chime the PSSE up.

fb599

 

[wilber]

Insulated cables are rated by a certain ampacity to keep the conductor and insulation at the rated temperature. End devices and conectors are usually rated at a temperature below the cables temp. Usually the rated temperature of the devices are 75C and the cable is 90C. Nothing delterious should happen below the rated temp of the device of cable.