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18 comments
Member

Join Date: Jan 2009
Location: Hyderabad
Posts: 8

Power Factor

01/17/2009 2:45 AM

Dear Members,

I have One quotation for Power Factor in my Company suddenly increased MD 1900KVA to 2731KVA without any additional loads.

At that time in sub-station all Capacitor banks are ON position. (Manual Mode)

At 6:00Am the MD is 1900KVA – PF-0.990, 29Amps at 11KV side.

At 7:15AM the MD is 2730KVA – PF-0.529, 50Amps at 11KV side,

Note: we have 132KV power supply from 220KV sub-station, at that time one of the 220KV power supply taken Line clearance. For maintenance at 220KV side. At that time power factor is decreased at 132KV main meter side. Is there any effect consumer side PF..?

Please any one explain Pl…….

Waiting for your replays……

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#1

Re: Power Factor

01/17/2009 4:46 AM

Something in your supplied data needs clarification please. Your 6am reading 29 Amps at 11KV implies something less than 320KVA, not the 1900KVA that you report. I suggest that you please have that data checked by your own staff.

Also, you describe one of the 220KV lines taken out for maintenance. If that was one phase line of a previously balanced 3 phase system, then your capacitors will be trying to provide 3 phase balance for a two phase supply and all sorts of strange reading could be seen if that wasn't correct for. Earth relative to neutral would be under challenge, the capacitors would be trying to "feed" reactance back into a non supply line and the meters might see that reactive current. Without SPECIFIC details of the complete power supply system from the supply lines, through transformers and your switchboard, any attempt to provide a specific answer would be only a guess.

With the cost of electrical power supply and the penalty for poor power factor situation, it's worthwhile getting a local specialist to look at this for you in some detail if you are in fact running at 1900KVA.

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#3
In reply to #1

Re: Power Factor

01/17/2009 5:47 AM

Thank You Sir,

I will be check,

Regards

BVREDDY.

Hyderabad.

India.

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#11
In reply to #1

Re: Power Factor

01/18/2009 6:25 AM

GA from. You said it first!!!

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Guru
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#14
In reply to #11

Re: Power Factor

01/18/2009 11:49 AM

Hi, Andy Germany!

I kinda like #6 for a creative approach to the fix, especially after V I Abraham ferreted out the extra loading on the system. G.A. to vinukumar for thinking about evening out the flow on both ends of the loop.

Mark

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#15
In reply to #14

Re: Power Factor

01/18/2009 12:12 PM

Thats allowed!!

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Guru

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#2

Re: Power Factor

01/17/2009 4:59 AM

220KV line is taken by the distribution man (Electricity supplier)

This will not have any effect on the power factor of the user.

You are likely to have two problems

a) As mentioned the removal of phase may have problem with your three phase capacitor bank. However if these are properly designed, then the compensation is done phase wise. I don't know the configuration of your pf compensator.

b) The single phasing/ heavy un balance in a 3 phase lines will have its own effect on the power factor of the system.

neither the compensators nor the motors (3 phase) will be able to cope up with it. There will be very high negative sequences and the compensatore are not designed to handle these nor are the motors.

In fact in our factory the aux breaker trips on single phasing (keeping the lights on offcourse).

the resistive loads are un-affected by the single phasing. It is surprising your machines didn't trip/ burn-out.

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Anonymous Poster
#4
In reply to #2

Re: Power Factor

01/17/2009 5:53 AM

Dear SB,

Thank you for yopur reply.

Regards

BVREDDY.

HYDERBAD

INDIA.

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#5

Re: Power Factor

01/17/2009 9:57 AM

Well, it appears that your power factor has suddenly changed and is to blame. The cause? Possibly a ground fault or a failure of the power factor correction equipment (if any).

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#6

Re: Power Factor

01/17/2009 10:52 AM

Dear Mr.Reddy

Obviously your load will record higher due to drop in supply side PF to extream low value. Your APFC system will take care of your connected load inductence and hormonics due to inductive and non linear loads, also will compensate your transformer inductive load for some extent. Consumer side Capacitor bank will not compensate the incoming PF drop. The obnormal recard of MD is only due to supply side PF drop. If you are still and continue to face the problem of this kind, to overcome this you have to install Capacitor bank in 11 KV supply side also

Regards

Vinu

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#9
In reply to #6

Re: Power Factor

01/18/2009 12:18 AM

Dear Vinu,

Thank you very much for your valuable answer,

Regards,

BVREDDY.

Hyderabad,

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#7

Re: Power Factor

01/17/2009 10:54 AM

Hi Reddy,

Welcome. Glad to note that you have registered as a member.

From the information given

6.00 reading of MD indicated as 1900 kVA. ( Do you have graphical recording instrument or any meter reader take MD readings at a specified interval and log it ) With out such an arrangement you cannot know when MD meter touched the highest value of 2730 KVA and how long it persisted.

At 7.15 AM you have noticed that MD touched the value of 2730 KVA. ( IF the information/data provided to you remain correct.

At 6.00 AM was your PF as stated was noted as 0.99

At 7.15 AM the PF was 0.529

What can be the possible reasons for this sudden jump in MD during this period.

I presume that this period could be the start of a shift. Too many heavy load might have been switched on simultaneously because of any specific reason which was not the practice in normal working days.( A VIP visit or specific production requirement , simultaneous starting of some heavy load which was non functional earlier or idle spare machine might have been put on use all on sudden .) The actual reason sudden increase in load needs investigation.

The sudden drop in PF value indicate the load that was switched on, is highly inductive like Induction Furnace / Large Induction motors etc. which further enhanced the the KVA further, as the KVAR has shot up due to low PF of system.

It is recommended that you must install a suitable APFC instead of Manual switching of PF for maintaining correct PF through all load condition.

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#8
In reply to #7

Re: Power Factor

01/18/2009 12:13 AM

Dear Sir,

I really appreciate your Exultant answer, on that day we have a specially program conducted in my campus, due to this reasons we have switched ON loads before, (compared to normal days) I have found that at that same time my Incoming 220 KV sub-station, there was One feeder taken shutdown, (assume is there any HT capacitor banks got trip is any reasons) at that time is there any effect to consumer side meter,

Because my company side all capacitor banks are ON position (Manuel Mode, I have checked with my team)

My quotation is incoming sub-station HT capacitor banks failure time is there any effect to consumer side PF,

Is there any grammar mystics please ignore…

Thanks & Regards

BVREDDY.

Hyderabad,

India.

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Anonymous Poster
#10
In reply to #8

Re: Power Factor

01/18/2009 2:08 AM

Hi,

just wondering if you may caused a leading power factor situation? You mentioned that the PFC was in manual and all capacitors were on, not sure why this would be done. But is it possible that your load at that time was in fact had a resonably good power factor and by switching on the capacitors and caused a PF of -0.55?

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#12
In reply to #10

Re: Power Factor

01/18/2009 7:24 AM

Dear Sir,

the PF is +0.55

regards

BVREDDY

Hyderaabad.

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#13
In reply to #12

Re: Power Factor

01/18/2009 8:32 AM

From memory only I hasten to add!, I assume that a "+" infers a leading PF, then that shows that then you are using too much capacitance for the load that you have!!!

No wonder your electricity bills have shot up!!!

A "-" PF then (Lagging or too much inductance) means too little capacitance......

The further away from 1.0 you go, the higher your "Real" costs will be due to "Apparent" power usage....

You must aim for 1.0 or Unity PF. Leading or lagging PF will both increase your costs without you using any more "REAL" power......someone must look at the PF Meter every time your load changes, to adjust the amount of capacitance to suit (as you only have a manual system if I remember correctly!).

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#17
In reply to #8

Re: Power Factor

01/26/2009 7:01 AM

The power factor of a consumer is dependent on its load alone and is not affected by its power supply power factor.

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Guru
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#16

Re: Power Factor

01/18/2009 9:15 PM

Since the currents, voltages, and KVA don't match, it is likely that the meters are not scaled properly and that the phases for current and voltages are inversed.

Make sure that phase A voltage is measured with phase A current at the same point as much as possible. Same for B and C.

I have seen power meter wit mixed up wiring giving strange results under certain loads and almost reasonable results other times. These errors can go un-noticed for years until somebody question the results.

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Anonymous Poster
#18
In reply to #16

Re: Power Factor

01/27/2009 5:58 AM

Dear Marcot,

Thanks

regards

BVREDDY

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Users who posted comments:

Andy Germany (3); Anonymous Poster (5); BVREDDY (2); Just an Engineer (1); marcot (1); MarkTheHandyman (1); myn1996 (1); sb (1); tropicalspeed (1); V.I.Abraham (1); vinukumar (1)

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