Harmonic filter for better power quality

[Anonymous]

fransjack123@yahoo.com is my email…

can i send you some more data and explain some of them for me?… active harmonic filter is new to me …

i need your experties here… thank you for the reply

[M R Srinivas]

Yes, please send data available with you, it will help us to design suitable solution.

[Anonymous]

have you received the data i sent you?

[M R Srinivas]

Yes, have received two documents, its quit exhaustive, will go through and reply shortly.

[rudy_budiantoro]

Hi Mr. Srinivas;

 

Can I have your opinion, please? Most of my customers only care about the energy saving that may result from installing AHF. If I talk about the heat loss, etc etc, they are not buying it because their plant is “so far so good”.

 

Recently I found that Fluke 425 series II come out with new feature where there is kWh saving potential due to harmonics. Do you have any concrete calculation/argument that energy saving is indeed obtained via AHF installation?

 

Thanks,

 

Rudy

[M R Srinivas]

Hy Rudy,

It is quite clear that the presence of harmonic will increase the kWh consumption in the network.

The excess energy consumption is due to the following:

a) Losses in the conductors/switchgears due to Skin effect.

b) Losses in transformers / reactors (Iron core) due to increased:

        –  Magnetostriction (Sound loss – you can hear more humming noise when harmonic is more).

        – Core loss.

c) Higher energy consumption in Rotating machines such as Induction motors, Generators due to Negative torque induced in the rotor winding when Negative sequence harmonic are present.

Other stray losses..

The problem is in quantifying or making the losses tangible. To do that it is important to have detailed analysis of each of the equipment in the network, which may be very tedious job.

In most of the cases, even if we quantify the losses, and if we install any harmonic filtering solution such as passive or active filters, the loss saved due to reduction of harmonic and internal losses in the filters may be almost equal.

Best regards,

[Anonymous]

thank you mr srinivas…. i owe you one.

[rudy_budiantoro]

Hi Mr. Srinivas;

 

Thank you for your input and advice. I personally think that the energy saving obtained is not as quantifiable as reducing the motor rpm. For pump and fan application (variable torque), reducing the speed meand reduced kW definitely.

 

I think after reading this forum, I will leave the idea of energy saving using AHF.

 

On the other hand, Mr. Srinivas, how can we “quantify” the effect of harmonics in our system for the case of breaker trip, motor wear and tear, and so on? This kind of losses cannot be proven with real demonstration. They only happen “occasionally”.

 

Or is there a way to trip a breaker by increasing the harmonics?

 

Your email will be highly appreciated, Mr. Srinivas.

 

Regards,

 

Rudy

[Jobmayo]

Hi Mr. Srinivas;

 

I am an Energy Consultant, also from the Philippines. I would like to know more about Harmonics Distortion and its negative effects to industrial and commercial facilities.Does it also affect the power factor?

 

We have a Fluke 1735 here with me but I still am trying to study more on how to interpret the graphs in the Harmonics Screen.

 

Also, our company is trying to put up an Energy Audit team. Can you give us any idea on how to begin with this?

 

Thanks,

[Anonymous]

Dear Sir, Can you please suggest/comment how to select a detuned filter when the system is polluted with 5th & 7th harmonic predominantly. Is it advisable to select a tuned filter separately for 5th & 7th? Please reply. Regards

[Anonymous]

Hi, K.R.,

It sounds like you are trying to correct for harmonics employing 5th and 7th harmonic tuned filters. This can be difficult and result in system issues if the total harmonic loads are more than 50% of the total loads.

In order to meet the cancellation capacity needed for 5th and 7th harmonic filters, it is very likely that the total displacement PF is corrected to leading. If the leading PF is substantial, the voltage will be increased to unacceptable levels for the connected loads (>10% of actual). This will be harmful to your loads – some may fault due to over voltage or fail completely.

Additionally, it is possible that safety devices and contactors begin to fail to operate. Leading PF causes contacts to become pitted as they are actuated. One result is that circuit breakers may fail to open or fail to close.

Another issue is that PF capacitor systems are designed to switch according to the displacement PF at the point of monitoring (where the CT is located). This does not assure that the proper amount of filtering steps are activated at the right times. It is possible that the 5th and 7th tuned filters are over loaded and suffer premature failure.

Finally, if additional loads are added to the network, the whole filtering/PF correction system must be re-examined for suitability of use.

We suggest that active harmonic filters be used when more than 50% of the total loads are harmonic producing. This may be more expensive but the system will not encounter any of the above issues. [Do remember to insure that 3-5% impedance reactance is installed at each harmonc rectifier.]

Regards, Jim

[Anonymous]

Hi Jim,

In regards to the Active Harmonic Filter. How would one size the filter with both linear and non-linear loads on the bus.

Example: With several non-linear loads with a full load amp rating of 225 Amps @ 480 Volts/60 hz and linear loads of 75 amps. Assuming 35% THD and wanting to be at <5% THD. What would be the proper calculation to find the corrective amps needed for an active harmonic filter.
Regards,
Johnny

[Anonymous]

Hi,
One of the substation we are facing issue hormonics more than 25THD, only when the load is very low(10amps& PF is unity). someone can explian how to mitigate the harmonics distoration.
Thanks,
Kali

[Anonymous]

Hi, Kali,

The information you have provided is very sketchy and makes it extremely difficult to provide good and pertinent comments.

As a general statement, you mention a substation with 25 THD. Is the THD measurement for voltage or current? If that is a THDv measurment, then you may have real problems. If that is a THDi measurement, then you may not have a problem.

If you are referring to a substation, I would expect the current to be much greater than 10 amperes as stated. For a substation 10 amperes is almost nothing.

Something to think about is that 10 amperes is a very small load. Depending upon the source rating (short circuit amperes – ShCA), the THDv should be almost 0% (1-2% would be typical background noise). If the ShCR (Short circuit ratio: ShCA/fund amental current of load) is very high, the THDv would be extremely low for a 10 amp load with 200% THDi.

Much more information is needed to better understand your situation. But I can say with much conviction that a 10 amp load is not going to be a problem….

Regards,

[Anonymous]

Hi Jim,

I thank you for giving the idea of Power Quality in Electrical Distribution System that leads to End users.

[Author]

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