IET
Decrease font size
Increase font size
Topic Title: CFL's & pf
Topic Summary:
Created On: 28 February 2011 11:35 AM
Status: Read Only
Linear : Threading : Single : Branch
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 28 February 2011 11:35 AM
User is offline View Users Profile Print this message



AdrianWint

Posts: 262
Joined: 25 May 2006

In an idle moment over the weekend I was looking at the real time power consumption of my house (I know.... I'm sad, I have a measurement centre sniffing the incoming tails which allows me to record P, Q & S amongst other things).

In particular I was surprised at how poor the power factor was (0.85). This was a Sunday eve with lots of lighting (mainly CFL), kids in there rooms on the PC, PS3 etc. This started me thinking that as we exchange the humble filament lamp (which has a pf of 1) for the CFL, which has a very poor power factor, how is this going to affect the distribution system?

Looking around my house most loads are electronic now, the only resistive loads of any size are the oven & immersion heater. I guess this is true for others too. 20 years ago we had a base load of hundreds of thousands of filament lamps bringing up the pf, now they are going.

As we all know, the old analogue meters could only measure the in-phase component of the current so we (domestic customers) only paid for the real power and didnt worry about the reactive. Modern electronic meters are more than capable of breaking down the power into its real & reactive components. Obviously, this reactive component requires reactive current to flow in the network which has implications for the DNO's, so.......is the day approaching whereby domestic customers will be encouraged to present a better power factor?

A topic for discussion perhaps?

Adrian
 01 March 2011 02:03 AM
User is offline View Users Profile Print this message


Avatar for sfchew.
sfchew

Posts: 589
Joined: 10 December 2002

The need for good power factor in residential buildings will be significant in view of the new appliances. It is either we push it to the manufacturers to comply or some automatic power factor correction like those in use for commercial and industrial buildings.

It will be a good idea to reward residential buildings that can maintain high power factor as an incentive.

Effectively it will be necessary to mandate 0.85 as a minimum PF and any improvement can attract some discounts in the bill.

Regards
Chris Chew
 02 March 2011 09:05 AM
User is offline View Users Profile Print this message



broadgage

Posts: 1308
Joined: 07 August 2007

Although CFL tend to have a low power factor, they are a very small load.
Electric heating appliances have unity power factor, and are probably much greater in total load.

Had you measured the power factor with the oven or water heater in use, it would probably have been at least 0.95.
 04 March 2011 08:51 PM
User is offline View Users Profile Print this message



Backintime

Posts: 282
Joined: 11 April 2007

Domestic customers pay around 16p a kWr. Non domestic customers pay a lot less. The supply companies will always make money.
 05 March 2011 09:50 PM
User is offline View Users Profile Print this message



williamjohn

Posts: 178
Joined: 22 November 2010

By kWr I presume you mean kWhr. Am I right in believing that domestic customers pay nothing for kVAr or kVAr hr. The old induction meter measured kWhr.

Regards
John
 05 March 2011 10:59 PM
User is offline View Users Profile Print this message


Avatar for sfchew.
sfchew

Posts: 589
Joined: 10 December 2002

Most domestic tariff will not include PF in their calculation. We are not focusing on the tariff charges but the effect of modern appliances that may cause poor PF. If CFLs do not have high PF we need to improve it for the sake of efficiency in power distribution.

Regards
Chris Chew
 07 March 2011 08:00 PM
User is offline View Users Profile Print this message



AdrianWint

Posts: 262
Joined: 25 May 2006

Although I agree with Broadgate - adding a considerable resistive heating load does improve the power factor, however it only does it for a small proportion of the time.

Its now a typical Monday eve .... dinner is over & the family has settled down for the evening pursuits ..... at the moment we are drawing 1.25kW, 0.49kVAr(ind) & 1.34kVA giving a power factor of 0.93. We also have significant THD at 30.3% of which 1.46A is third harmonic (ie. 25% of the fundamental). Looking at the current waveform - it is nowhere near a smooth sinewave!

If my house is typical of others in the street there must be significant reactive currents flowing in the street distributor as well as considerable third harmonics in the neutral, both of which wouldnt have been there 20 yrs ago.........


Adrian
IET » Energy » CFL's & pf

Topic Tools Topic Tools
Statistics

See Also:



FuseTalk Standard Edition v3.2 - © 1999-2014 FuseTalk Inc. All rights reserved.