Typical Load Power Factors of Urban Areas with A/C

[kartracer087]

Hello,

I am curious to know what the typical load power factors have been estimated for urban loads (commercial buildings and some residential towers). Reason why I ask is I've seen a number of urban substations that do not have power factor correction installed at the substation or inside transformer vaults, so it is safe to presume the full load power factors are generally high in urban environments (0.9 and above maybe)? Speaking generally of loads in the USA in larger cities which have air conditioning.

Thanks.

 

[waross]

Are these newer substations with lots of spare capacity?
There may be plans to add PF correction in the future as the load increases.
Don't spend the money until you have to.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Gr8blu]

Kartracer087: As waross pointed out, the idea might be that the substation is oversized for the existing residential load - and will have PF correction added later. It is also possible that the geography and weather patterns mean that although there might be HVAC loads at some times of the year, it isn’t really the norm (think Minnesota). I suspect that where there is heavy usage (think Texas or Arizona), the likelihood of lower power factors exists with higher inductive loading.

Also consider the number/size of non-linear loads (electronics, variable-speed applications, ballasted lighting, dimmer switches, etc.) that might be part of those urban load groups. Chances are an area with (or expected to have) higher non-linear load totals will have some additional PF correction capacity.

Converting energy to motion for more than half a century

 

[cuky2000]

My guess is that PF is in the 90% since many pieces of equipment have some capacitor correction. See the partial list below.

 

[kartracer087]

Thanks, yes I think what is happening more so with larger buildings and commercial buildings in particular is that you are seeing more electrical loads that indeed do have built-in power factor correction in their controllers or power supplies because they need harmonic filtering. An example is a refrigeration chiller for a high-rise AC. Modern chillers often have variable frequency drives installed in them and those often have harmonic filters with large capacitors. The load power factors on those can exceed 90% power factor at full operating load. In addition, as mentioned with other computers, LED lighting, and smaller loads having internal capacitors in their power supply circuits, the power factors of those loads are rising. Doing a survey of mid-rise commercial buildings, one at a corporate campus with a new chillers, LED lighting, and office loads, their combined metered power factor was about 95% at the summer peak load point. I think this explains why I've seen in a few areas why some power companies are able to remove capacitors from substations as their customer load power factors rise with replacement of older equipment. I know its generally not good practice to over-correct with extra capacitors if it is not necessary.

I know data centers which are primarily filtered switched mode power supplies, most all motors are on filtered VFD's including the chillers, it is not uncommon to have unity power factor (in some cases even leading!).

Now, harmonics is a different story as those have risen to some extent, but talking about purely capacitive or inductive power factor and not displacement power factor considering harmonics, it has been improving.

 

[jghrist]

It is better to add capacitors out on the distribution line instead of in the substation. This way, line losses and voltage drops are reduced.