Overloaded Capacitor Bank

[Riyad]

Dear all, I have capacitor banks overloaded morethan 130% (as per IEC). What action shall I take?How to rectify?

Kindest regards,

 

[bob]

Dear all, I have capacitor banks overloaded morethan 130% (as per IEC). What action shall I take?How to rectify?

Kindest regards,

Overloaded as in voltage too high or current too high?

 

[ramdiesel3500]

How do you overload a capacitor bank???

 

[jtester]

I don't see how a cap bank can be overloaded unless it is subjected to too high a voltage.

Jim T

 

[Riyad]

Vide IEC831-1

Vide IEC831-1

Dear all,
According to IEC831-1, capacitors have permissible thermal current(RMS) of 130% of rated current. And what I have are of more than 130%.

If understood please, answer my question above?

Kindest regards,
Riyad

 

[LawnGuyLandSparky]

What?

Occupation:
Electrical Rnginner

 

[bob]

Dear all,
According to IEC831-1, capacitors have permissible thermal current(RMS) of 130% of rated current. And what I have are of more than 130%.

If understood please, answer my question above?

Kindest regards,
Riyad

Is the voltage at the correct level? If so, I would investigate harmonic contribution.

 

[ghostbuster]

If you do not have the ability to measure the harmonic frequency current contribution,use two clamp-ons.The trick is to use an old old amprobe style that measures 60 hz. current and a new true rms clamp-on.The difference will give you a "rough" idea if harmonic currents are present and overloading the cap.

 

[bob]

Riyad
Do you have variable speed drives at your location?

 

[Riyad]

Yes,
we have frequency converters (two) and UPSs in the system. I ahve measured the THDV and THDI for some capacitor banks thru RVT (PF controller) and found that THDV= 1.6% and THDI= 41.6% and calculated the loading%= 158% (Irms/Irated). I noticed in some capacitors that even harmonics are more than odd ones.

Please advise.

Kindest regards,
Riyad

 

[davidr43229]

what exactly do you want to do with these overloaded Capacitor Banks ?

 

[ghostbuster]

Yes,
. I noticed in some capacitors that even harmonics are more than odd ones.

Even harmonics are normally generated when the rectifier ccts(etc.) are not firing symetrically.I would recommend you check these circuits for non-symmetry operation.Correcting this firing problem should significantly reduce the cap overloading situation.

 

[wirenut1980]

Even harmonics are normally generated when the rectifier ccts(etc.) are not firing symetrically.I would recommend you check these circuits for non-symmetry operation.Correcting this firing problem should significantly reduce the cap overloading situation.

I have read that even harmonics can be caused by 3 pulse rectifiers, and to get rid of these, you either have to switch to 6 pulse or 12 pulse rectifiers, or install harmonic filtering at the load.