Neutral Current for CAPACITOR Unbalance Protection 1

[afzumannu]

Dear Engineers,

We have Filter bank line voltage is 33 KV ( 33000V), ungrounded double star connection. capacitors are connected series parallel group. each phase one row is connected to star1 and other row is connected to star2 , unbalance CT is connected in between both star point. i want to know what is the formula for neutral current flow so can understand the % of unbalance.
i know one formula that is Iunb = ( I1+I2+I3)-(I4+I5+I6), I1,I2,I3 is one star side each phase, while I4,I5,I6 is other star side. also Iunb = Un/Xc, so i will apply the values in this formula which. I have recorded the values for Xc1 = 27.2231µF, Xc2 = 27.2499, Xc3 = 26.6247 ( one group), Xc4 = 26.6499,Xc5 = 26.7749, Xc6 = 26.7747(2nd group), hence Xc=1/2πfc, here i want to know from you guys What is Un here is it 33000 V supply voltage? or individual Capacitor name plate rating, 15000V, 459 KVAR, or someone can calculate the neutral current here, any other formula let me know.

 

[afzumannu]

@ beyond i prepared the model including the resistance i am attaching herewith but the values are not coming, something wrong?
what is the source resistance and source inductance? from where these default values we are getting? also if i am changing the source resistance or inductance in my old slx file ( first u send) the current values changing.

 

[afzumannu]

@Anoter,
Yes in Matlab they are using the default values of source resistance 0.8929 Ohm.and source inductance 16.58mH.
If i am changing these value the neutral current values changing. i think we have to calculate that way. how we can find out manually these values?

 

[afzumannu]

Hi Guys,
Still I am looking for the Manual calculation except Matlab for these capacitor banks neutral current. Mr. beyond answers were very similar to the actual value. I am requesting @Anoter, @Argotier and others please come forward to solve this. thanx

 

[davidbeach]

No, you solve it. You’ve been given Tips. This isn’t a site to have others do your work for you.

 

[afzumannu]

Dear @Argotier and @Anoter can you attach the Excel sheet which you made, now results are coming correctly. thanx

 

[afzumannu]

@ Mr. beyond, in Matlab simulink you put the source resistance and source inductance values, resistance 0.8929Ω and inductance 16.58mH, from where this values you calculated? by using these values results are fine, but if i remove these result different, can you specify please?

 

[afzumannu]

@ Mr. Beyond source Resistance & source Inductance these values for all the circuits? as you put the same value in both the Files, please clarify me only this, i am waiting reply.