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Harmonic Filters For Pfi Capacitors


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#1 AB2005

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Posted 16 March 2014 - 06:31 AM

Dear Mark;

 

In our 800Kvars PFI system where 16 capacitors (Nokian brand) each 50kvars are installed, there is no any harmonic filter is connected with any capacitor. In our Corrugator plant, there are many DC and AC drives which create harmonics in line. So an expert recommended as to connect harmonic filter on each capacitor to protect it against damage/burning. As I don’t have any experience with harmonic filters in past, your help require to select the required filters.

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#2 mariomaggi

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Posted 16 March 2014 - 07:14 AM

Dear AB2005,

to understand better the situation of your plant and to give you better suggestions, it would be useful to know something more about types and dimension of loads, size of power transformers, lenght of lines, contemporaneity factor for non-linear loads, etc.

It is also interesting to know if the plant is new or if it is working for years without problems.

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Mario


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#3 marke

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Posted 16 March 2014 - 07:54 AM

Hello AB2005

 

I would only consider the use of d-etuning reactors if the bere is sufficient harmonic voltage present to drive harmonic currents through the capacitors.

 

This can easily be proven by measuring the total current into the capacitors. If the current is 10% or more than the correct current for the capacitance and voltage, then you do have harmonic voltages and harmonic currents and de-tuning reactors should be fitted.

 

Before you fit de-tuning reactors, you need to ensure that the capacitors are designed to be used with de-tuning reactors. De-tuning reactors and harmonic voltages cause the voltage across the capacitors to increase and while the KVAR rating may be based on a supply voltage of say 415 volt, the continuous voltage rating of the capacitors needs to be in the order of 525 - 600 volts for a 400 Volt installation.

 

De-tuning reactors increase the costs and also the losses in the correction system. This results in a considerable increase in the heat to dissipate from the enclosure.

 

First, determine if there are harmonic currents flowing in the capacitors by measuring the capacitor current.

Second, if the currents are too high, then determine if the capacitors are rated for use with de-tuning capacitors. If not, you need to replace the capacitors with capacitors suitable for use with de-tuning reactors.

 

Best regards,

Mark.



#4 AB2005

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Posted 17 March 2014 - 11:15 AM

Dear Mark;

 

As the existing capacitors are each 50kvar 69.5A. So when i measured the current of 5 capacitors, that was 69.6A, 68A, 66.7A, 66.7A and 68A. It means there is no harmonics present in line.


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#5 marke

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Posted 17 March 2014 - 05:56 PM

Hello AB2005

 

That would be my interpretation unless the capacitors are failing and losing capacitance and so not showing an increase.

 

Best regards,

Mark



#6 AB2005

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Posted 19 March 2014 - 08:12 AM

So conclusion is that we are not needed to install Harmonic filters. ok?


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#7 marke

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Posted 19 March 2014 - 09:00 AM

Correct






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