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Anonymous Poster #1

11 kV Busbar current rating.

01/21/2022 5:49 AM

Dear sir,

Please helpme in finding out busbar current rating when there is 27.3 MVA generator, generation voltage 11 kV, This gives a current rating of 1432.9 amps with 20% safety margin gives 1719 amps. Can we keep 2000 amps of busbar rating? but i am worried if for a sub-transient reactance of 15% would increase initial subtransient current to eleven thousand four hundred sixty-three (11,463 amps). Can busbar withstand this current? or this is handled by fault current rating of busbar.

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#1

Re: 11 kV Busbar current rating.

01/21/2022 7:46 AM

Most design protocols call for a second-person check before they are issued for construction.

So far, the thread begs the question as to whether there are sufficient qualified persons at the facility to ensure robust designs are coming out of it.

One also might wonder how many <...Anonymous Poster #1...> threads are coming of late from the same origin.

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#2

Re: 11 kV Busbar current rating.

01/21/2022 8:01 AM

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#3

Re: 11 kV Busbar current rating.

01/21/2022 8:37 AM

Based on the limited information you provide, 2000A continuous rating of the bus is adequate, with considerable margin above your specified generator current. The fault rating of the bus will be determined by the manufacturer, based on the information you provide about your expected available fault current. If you provide those who are bidding to furnish your switchgear with the fault current information you provided above, they will offer you switchgear that is rated to handle it. That's who you should be talking to about this - the switchgear manufacturers.

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#4

Re: 11 kV Busbar current rating.

01/21/2022 1:12 PM

If you have the 2000 A busbar geometry you may verify if the busbar withstands the thermal and dynamical effort according to IEC 60865-1. However, I agree with Piter T: the manufacturer here has to be the decider.

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#5

Re: 11 kV Busbar current rating.

01/22/2022 12:15 AM

When it comes to fault rating, the calculation has to take in to account the grid contribution as well, assuming you have grid supply also connected to 11kV bus.

You can verify the calculation further.

However, for a 2000A busbar, fault rating of 40kA, 1s is not an issue.

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#6

Re: 11 kV Busbar current rating.

01/22/2022 4:10 AM

"Can we keep 2000 amps of busbar rating" suggests that you have busbars already in place. Check the specification and fault rating of the existing bars to determine if they are suitable. If not, employ a 'competent person' to calculate your upgrade.

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#7

Re: 11 kV Busbar current rating.

01/24/2022 7:44 AM

Undefined: <...we...>.

If in doubt, consult a local qualified Electrical Engineer.

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