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Life of RC Filter capacitor

09/23/2011 8:05 PM

There is RC filter unit for 28MVA Transformer. there was a blast in power capacitor and fired was occured due to oil in capacitor.

now i want to know that what is the life of power capacitor. time base replacement is possible ? if yes then on what basis - like value of capacitor ? is aging effect on capacitance of capacitor ? is capacitance increase or decrease with aging effect.

how can i know that now this capacitor is going to be faulty. is there any measurable parameter?

plz reply.

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#1

Re: Life of RC Filter capacitor

09/23/2011 9:02 PM

How about taking it off line and doing a load test on it or them. Then create a log of your findings and a PM program to follow.

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#2

Re: Life of RC Filter capacitor

09/23/2011 10:38 PM

Measure the leakage resistance or current and compared it with value when it is new. As capacitor age, leakage increases, more leakage, more i2R heating until the temperature reach the flashing temperature of the oil and explode.

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#3
In reply to #2

Re: Life of RC Filter capacitor

09/24/2011 2:49 PM

Thanks for reply, but is it possible to know the condition of capacitor base on it's capacitance ?

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#4
In reply to #3

Re: Life of RC Filter capacitor

09/24/2011 11:05 PM

Capacitor are built usually with tolerance +/- 10 to 20 %. Although aged capacitor will show reduction in capacitance , you will not know for sure unless you measured the zero hr value.

A better and surer indicator of degradation of capacitor is still increase in leakage current, compared this with spec. More leakage, worst degradation.

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#6
In reply to #4

Re: Life of RC Filter capacitor

09/25/2011 2:22 AM

What is the maximum % tolerance allowable in Capacitance,leakage resistance,current taken etc compared to zero-hour value as per regulations(BS/IEC/NEC etc)?.

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#7
In reply to #6

Re: Life of RC Filter capacitor

09/25/2011 3:22 AM

go check regulations(BS/IEC/NEC etc)

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#9
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Re: Life of RC Filter capacitor

09/25/2011 8:57 PM

In some countries people from outstations,especially from the regions where racial minority hails from, are forced to live in the capital city as all engineering and other offices are located in the capital. So if an engineer earns USDollars 300 as monthly wages and pays that 300 dollars as house rent will he have any money for downloading literature?. In this forum many experts have given either links to download or at least the reference numberr of the standard or quoted from regulations/codes

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#5

Re: Life of RC Filter capacitor

09/25/2011 12:38 AM

A rough rule of thumb is that a capacitor bank will lose about 1% of its efficacy per annum.

A 16 MVAr/132 kV bank I was running lasted 16 years but began to develop serious out of balance problems.

If the capacitors are internally fused there is no real, external, indication of deterioration as the fuses blow over the years and the interphase current should be closely monitored. If you can take the bank out of service the capacitors can be disconnected and their capacitance measured and, perhaps rearranged to rebalance the phases.

But at some stage the total capacitance will change to the extent that it effects the resonance frequency of the bank and you may run into serious harmonic issues.

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#8
In reply to #5

Re: Life of RC Filter capacitor

09/25/2011 3:25 PM

Good answer and welcome to CR4....

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#10
In reply to #8

Re: Life of RC Filter capacitor

09/26/2011 2:09 AM

Thank you nice to be here

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