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Old 16th February 2015, 16:40   #16
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Default Re: DeEnergia - Power factor correction device

I am bumping up an old thread. Tamil Nadu Govt has decided to change all utility meters to digital types ostensibly to improve TNEB's financial conditions. The new digital meters will be sensitive enough to detect the power consumption of small devices like mobile phone chargers.

I have observed one such digital meter fitted in my premises and it shows - Volt, Ampere and Power Factor along with the usual consumption. It also shows time and date ( this information it seems to download from somewhere as when there is a power interruption and on resumption, it briefly doesn't show the time and date.)

Our office UPS shows a power factor of 0.68 most of the time. Should I add PF correction capacitor to lower the overall bill as 'seen' by the new meter ? I know that the old meter showed only the energy consumption KWH and didn't have a clue about reactive power. I am not sure about the digital meter. It may calculate the reactive component.
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Old 16th February 2015, 16:46   #17
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Default Re: DeEnergia - Power factor correction device

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Originally Posted by Prowler View Post
Our office UPS shows a power factor of 0.68 most of the time. Should I add PF correction capacitor to lower the overall bill as 'seen' by the new meter ? I know that the old meter showed only the energy consumption KWH and didn't have a clue about reactive power. I am not sure about the digital meter. It may calculate the reactive component.
Today typically I think the Power company has a generic guideline on power factors to be not below a particular value. Thats more to do with not wanting to inject reactive power back into the grid and to de-stabilize it. But from a billing point of view I guess many have been using correction capacitors to reduce their bills. Dont know how it works with the billing companies.
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Old 16th February 2015, 17:04   #18
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Originally Posted by Prowler View Post
Our office UPS shows a power factor of 0.68 most of the time. Should I add PF correction capacitor to lower the overall bill as 'seen' by the new meter ? I know that the old meter showed only the energy consumption KWH and didn't have a clue about reactive power. I am not sure about the digital meter. It may calculate the reactive component.
If your office UPS shows 0.68 PF, and if you haven't been penalized for it, then it doesn't matter.

If you have a HT yard, that means you own and maintain your own transformer, then you are the only consumer of that transformer. In such case you must maintain the PF at 0.9 or more. Considering you are getting away with 0.68, you must be on LT, a shared transformer. Then you don't have to maintain the PF, and you won't be penalized for low PF either. It makes no difference to your bill, just your conscious.

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The new digital meters will be sensitive enough to detect the power consumption of small devices like mobile phone chargers.
This is new to me, you mean older meters can't measure the current drawn by mobile phone chargers?
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Old 16th February 2015, 18:18   #19
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Default Re: DeEnergia - Power factor correction device

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Today typically I think the Power company has a generic guideline on power factors to be not below a particular value. ..
But from a billing point of view I guess many have been using correction capacitors to reduce their bills. Dont know how it works with the billing companies.
Thanks Ampere. Looks like I would have to try some capacitors and monitor the result.

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Originally Posted by Samurai View Post
If your office UPS shows 0.68 PF, and if you haven't been penalized for it, then it doesn't matter.
Considering you are getting away with 0.68, you must be on LT, a shared transformer. Then you don't have to maintain the PF, and you won't be penalized for low PF either. It makes no difference to your bill, just your conscious.

This is new to me, you mean older meters can't measure the current drawn by mobile phone chargers?
Thanks Samurai. My earlier house had a 3 phase meter which didn't bother much with small loads less than 10 VA provided that was the only load. It seemed to have some 'inertia' which was overcome only when a larger load was activated. Most TVs and electronic appliance would draw low power under quiescent conditions. The new generation digital meters are sensitive enough to take these low power consumption into account - I gather.

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Old 8th November 2015, 18:48   #20
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Default Re: DeEnergia - Power factor correction device

This is absolute pure utter cheating!
Such people have been selling this idiotbox for around the same price (Rs. 3000/-) until some time back, openly advertising and marketing as a "power saver" equipment. Now it seems they changed the formal name as 'Power factor corrector' so legally they can play safe.

I happened to visit the same exhibition (VeeT വീടു്) today at Thrissur. The same product is being marketed and sold there. There are no claims of power saving in any labels, posters or leaflets. But the guys sitting there tell people that this will save upto 30% of their energy bills.
The fact is that this is just a capacitor inside which may cost Rs. 100 or 200.
It is not going to save any of your energy bills not even by a rupee.

The KWH meters installed in our homes are pure KWH Meters. They are not measuring our KVA.
KVA = Current x Voltage. But when current and voltage is not in phase, there is a vector difference between them which is called Power Factor. Ideally, the Power Factor should be 1 (Unity). But in AC loads, if you have lots of inductive machines (such as motors, welding sets, compressors etc.) the PF can be lesser (normally lagging).
With less PF, The actual power consumed (KW) is not as same as the product of Voltage and Current (KVA).
KW = KVA * Power Factor.
The Energymeter in our homes measures only KWh, the actual power consumed, regardless of the Power Factor.

In brief, the advertised idiotbox WILL NOT HELP YOU SAVE YOUR ENERGY BILLS!
IF YOU BUY THIS CHEAT PRODUCT, YOU WILL ONLY LOSE YOUR HARD EARNED MONEY TO SOME FRAUDS.
So not only that you do not buy this, but also PROPAGATE THIS INFORMATION TO WHOMEVER YOU MAY KNOW. You will be doing a great service to your fellow-citizens.
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Old 9th November 2015, 00:01   #21
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Default Re: DeEnergia - Power factor correction device

I went through this entire thread only now. It seems there is so much of misconception regarding Energy Meters, Power factor and Power consumption.

I am an Electrical Engineer with 30 years of thorough experience in energy systems engineering as well as other fields of electrical and electronics.

Let me try to jot down the important technical points in a simple way:

1. The Energy meter at our homes (and such small loads) are KWh Meters. They measure the actual energy used up in our devices. They do not add the fictitious power (reactive power KVARh) to their reading.

2. KWh and KVA are same in case of DC circuits. But in AC, it depends upon the relative amount of Inductance L or Capacitance C with respect to the pure resistance R in the overall load.

If there is no inductance or capacitance, the Power Factor is 1 (technically, PF is the the cosine of the angle at which Voltage V lags or leads the Current I in a vector/phasor diagram).
PF can also be thought of as the ratio of the Inductive or Capacitive Reactance to the overall Impedance (i.e. the seemingly effective 'resistance' of the load). Again, PF is also equal to the KW / KVA.

If the PF is due to too much capacitance, then we call PF is leading. If it is due to Inductance, then Lagging.

KW is the real power consumed. KVAr (KiloVoltAmpere-Reactive) is the fictitious power component. KVA is the overall apparent power. In Electrical Engineering calculations, they will always form a Right angled triangle, in which, KW is the horizontal arm (typically longer), KVAr the (shorter) vertical and KVA the longest, hypotenuse arm.

3. Most of the loads in our homes used to be more inductive. Old types of Ballast tube lamps, motors, some fans etc. used to be inductive. But more than that, our power suppliers used to have inferior circuits (overloaded and undervoltage) which makes the incoming supply itself with poor lagging PF (say 0.7 or so.).
Low PF is a problem for the supplier. They need to push more current and voltage for the same real energy they transmit. The extra component due to this extra V,I is called reactive power. This is really not used up. Instead it just keeps floating to and fro through the entire power grid, only producing extra current. That extra current will make an I2R loss in the transmission lines.

So, for the supplier, it is better to have the vertical KVAr arm of the triangle as short as possible with respect to the horizontal KW arm. (Don't bother if you don't get it ) .

4. At our homes, equipments works at their (any) PF anyway. They consume some real power. This power / Energy (KWh) is recorded in our meters. By the very design of the meter, KVARh *WILL NOT BE*recorded!

5. So, using any PF Correction at our home circuit does not help us save any energy or energy bills. But in a perfect world, if all the consumers had exactly One PF (Unity PF or UPF), it will help the supplier save a portion of their transmission losses. (If you overcompensate, the PF will turn to leading and that will again bring more transmission losses).
6. Our electrical infrastructure is generally much better these days. Most substations have properly rated transmission lines and huge capacitor banks to compensate for any loss of PF. Our home equipments are also well made to take care of PF as far as possible.

7. Therefore, the device being marketed as shown above, at a huge price (Rs.3000/-) (which actually contains only a normal capacitor costing around Rs. 100 inside) is a completely bogous cheatbox. In fact, our Government and concerned authorities should take care of such daytime robberies.
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Old 9th November 2015, 08:58   #22
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Default Re: DeEnergia - Power factor correction device

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Originally Posted by turbovp View Post
...

...The Energy meter at our homes (and such small loads) are KWh Meters. They measure the actual energy used up in our devices. They do not add the fictitious power (reactive power KVARh) to their reading.
...... This power / Energy (KWh) is recorded in our meters. By the very design of the meter, KVARh *WILL NOT BE*recorded!...
@turbovp : That is an excellent crisp explanation. Thanks a lot.

Can you also please share how the household meters are able to record only kWh and ignore KVARh ? What is the technique behind it ?

Does the same logic for industrial consumers too ? Do they also pay only for the active power ?
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Old 9th November 2015, 12:16   #23
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@turbovp :
Can you also please share how the household meters are able to record only kWh and ignore KVARh ? What is the technique behind it ?
The conventional energy meter is adorable for its rather simple logic. The fact that it can only measure true power comes automatically from that simple idea. For someone familiar with basic electric engineering facts, this is easily understandable.

You know
1. Power P = V x I
2. Energy = Power x time.

In case of AC circuits, the Voltage and Current may not be in phase. The actual magnitude of power is a dot product of the two vectors.
Therefore,
3. True Power = V x I x Cos ɸ
Where ɸ is the 'phase angle' (The angle between the Voltage phasor and current phasor.

Now, the KWH Meter is actually a kind of Induction meters with two coils. The Pressure coil (or Voltage coil) and the Current coil. These two coils are fitted in such a way as to produce a power. Naturally, this power will be equal to VI Cos ɸ. Using this power, a thin aluminum disc is rotated. Its angular displacement will be proportional to the power itself. So, connecting this disc to a train of gears, ultimately leading to calibrated numbered dials will give the VI Cos ɸ x time Which is the quantity of Energy.

Nowadays, this electromagnetic system is being replaced by solid state electronic equivalents. Instead of the moving disc mechanism, electronic transducers measure instantaneous values of voltage and current, which yields all the required quantities through a smart digital signal processor. The true power is then calculated by electronically processing V I Cos ɸ.

In fact, it is more cumbersome to measure the fictitious power (or energy - really there is no energy there!) than to measure the true power/energy itself.

You can see a well illustrated and simple page on this here: http://electrical-engineering-portal...e-energy-meter

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Does the same logic for industrial consumers too ? Do they also pay only for the active power ?
The measurement of energy for industrial loads are again based on three separate parameters: The True energy, Reactive energy and Maximum demand. They will have three separate meters to this effect.

The reactive power (which is floating between the substation and end-user points) causes an extra voltage drop (I x R) in the transmission path. This will cause an energy loss IČR that is measurable only at (and costing to) the suppliers end. The consumer has to compensate for this energy loss. That is why reactive meter (KVArh meter) is necessary. For small loads, this loss is not significant enough to justify an additional (and costly) meter.

The maximum demand is a peak recorder of the power at which time, the load was maximum during a billing cycle. It ensures that the consumer does not go beyond a stipulated level of consumption (which will stress the supplier's system beyond their generation / transmission capacity.

Many times, the real challenge for an electrical energy supplier is not their continuous overall generation capacity, but the instantaneous peak loads. At peak loads, they have to suffer not only stressed transmission network but also excessive and wasteful transmission losses.

Hence, the newest trend is to implement time-of-the day smart metering systems where you will pay more for the energy at certain time of the day when overall consumption is high (say evening) and pay low when the demand is low (say hours of late night or early afternoon).

Last edited by Samurai : 9th November 2015 at 12:55. Reason: back-to-back post
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Old 9th November 2015, 17:52   #24
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Default Re: DeEnergia - Power factor correction device

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Hence, the newest trend is to implement time-of-the day smart metering systems where you will pay more for the energy at certain time of the day when overall consumption is high (say evening) and pay low when the demand is low (say hours of late night or early afternoon).
For a long time UK homes have been able to get two meters. They get the energy used in the night at a substantially cheaper rate. I think it started when "storage heaters" (horrible, inefficient, uncontrollable things that should never have been invented. let alone installed) were a big thing. Heated up over night, at cheap rate, they gave off heat during the day.

The went out of vogue, but automatic washing machines with digital timers, and stuff like that, came in.
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Old 9th November 2015, 21:30   #25
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Default Re: DeEnergia - Power factor correction device

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For a long time UK homes have been able to get two meters. They get the energy used in the night at a substantially cheaper rate. I think it started when "storage heaters" (horrible, inefficient, uncontrollable things that should never have been invented. let alone installed) were a big thing. Heated up over night, at cheap rate, they gave off heat during the day.

The went out of vogue, but automatic washing machines with digital timers, and stuff like that, came in.
Yes, in the UK and in other European countries such as the Netherlands, Sweden and Germany we have had two meters in most houses for decades.

The idea is to encourage people to run dishwasher, and washing machines at night rather then during the day. this helps spread the load on the grid and makes it a bit more efficient, hence the lower price at night.

Jeroen
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Old 10th November 2015, 00:31   #26
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Default Re: DeEnergia - Power factor correction device

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Originally Posted by Jeroen View Post
Yes, in the UK and in other European countries such as the Netherlands, Sweden and Germany we have had two meters in most houses for decades.

The idea is to encourage people to run dishwasher, and washing machines at night rather then during the day. this helps spread the load on the grid and makes it a bit more efficient, hence the lower price at night.

Jeroen
Instead of having two separate meters as was in use for decades, now we can have a single intelligent meter that can be even programmed (and reprogrammed periodically as the power costs vary) on a time slot basis. (For eg. in UK, there is a unique 'tea-time' power surge that lasts for a few minutes every night! Read about this at http://www.bbc.co.uk/britainfromabov...ebritain.shtml. ).
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