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Ali18
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Join Date: May 2008
Posts: 136
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a Q

08/02/2011 10:45 AM

Hi guys

We have a number of 30/11 Kv power substations which are interconnected by underground cables as a loop form, one of these substations has a problem in a 30Kv cable, It's charged with 30Kv but unloaded ( connected from one side).. as it's unloaded, then theoretically it has to show a value of zero current (0 A) , although, it shows 10A on the measuring indicator and P = 0 MW, Q= 5 MVAR & then S= 5MVA, …. What's the cause behind that ?and from where did we get such amperage figures?...... Keep in mind that this cable had repeatedly been tested by a maintenance crew,

awaiting,.....

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PWSlack
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#1

Re: a Q

08/02/2011 10:48 AM

AC or DC?

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Ali18
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Join Date: May 2008
Posts: 136
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#3
In reply to #1

Re: a Q

08/04/2011 6:25 AM

definitely Ac,....

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Anonymous Poster #1
#2

Re: a Q

08/02/2011 5:24 PM

Of course it's AC...

I'm no expert, but here is my best guess. To have a measurement of reactive power you need some sort of capacitance or inductance. The reason I believe you are measuring 5MVAR's is due to the capacitance of the transmission line. You say it is still charged at one end so the cable is definitely storing energy. As for the 10A for there to be any reactive power, there needs to be current (the A in MVAR). Due to the reactive capacitance from the cable a current is drawn.
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