Bad Power Factor 1

[fredpar]

We are a small/medium size utility company (60000 customers) with some customer with bad power factor(i.e.: 0.6, 0.8). What can we do to fix this other than charge them for KVAR?
Thanks in advance for your ideas!

 

[davidbeach]

You can charge them for power factor. You can give them power factor correction caps. You could install caps on your distribution lines. Best bet would be a combination of power factor charges and caps on the distribution lines. Giving away power factor correction equipment would be robbing your other customers; power factor penalties used to pay for line caps would be the fairest solution.

 

[whycliffrussell]

Solutions:

1. Charge them for electrical demand (ie: bad power factor). If you have any industrial/commercial customers who run large motors this may encourage them to use their motor loads to correct the system power factor (ie: over excite their motors).

2. Install power factor correction caps (Personally I'm not a big believer in caps as they sometimes can be a greater danger than anything...especially if not 'oversized' correctly for fault/transient situations...)

3. Hook up some unloaded motors yourself to the system and overexite them (ie: synchronous condensor)

4. Hook up a SVC (static var compensator)...This is probably the most expensive, and complicated solution...however it would correct power factor and provided good voltage regulation for power factor variations.

I guess it really depends on your customers...ie: residential, commercial, industrial. For commercial and/or residential 2 and 4 would be the best options...2 being the cheapest of course. For industrial customers 1 is a good option...industrial customers typically don't like to pay too much for power so it would probably pursuade them to take matters into their own hands to correct the power factor as seen from their facility.

Like I said...even though I'm not a huge fan of caps, it's probably the cheapest and most feasable option...depending on the MVA of your load that is.

 

[bacon4life]

whycliffrussell
Could you please explain more of what you mean by "oversized" for fault conditions? I am familiar with possible harmonic/resonance issues and high voltage under low load conditions, but the only fault/transient issues I have heard of are outrush (which can be solved with outrush reactors) and self excitation of motors (which happens when capacitors and motors are isolated by the same protective device).

 

[ScottyUK]

Describe the utility network a little: is it a star topology with many long feeders radiating from a generating or distribution hub? An interconnected grid? How are the loads distributed geographically? Are there a few major load centres, or is it numerous small loads (e.g. farming community?). The structure of the network will make a substantial difference to the best way of dealing with the problems. Where do you need to correct? What equipment is the limiting factor: is it the individual lines which have inadequate capcity, or the generation / bulk supply point connection to the HV transmission network? Also, we have assumed that the bad PF is lagging. Is this the case?

----------------------------------

I don't suffer from insanity. I enjoy it...

 

[whycliffrussell]

Scotty:

You're correct about the outrush, however, depending on the type and loacation of the fault wrt to the capacitor bank, it may experience large transient overvoltages (voltage spikes) and large voltge swings at a fast rate dV/dt ... capacitors are designed to sustain an electric field across their plates, when this is exceeded bad things happen (ie: popping and explosions)

 

[fredpar]

Scotty:
Thanks for answer this thread. Yes it’s a star topology with two miles long feeders. We have two main loops on 69KV, nine subs. Most of our system is in the city and part of it in the county.
We do have enough caps in our 13.2Kv system to keep a decent power factor, but anyway we do have businesses with bad power factor. I’m going to list some of them:
Type of Business: Power Factor:
1) Golf Club 0.810
2) Store 0.871
3) Car wash 0.887
4) Dry Cleaners 0.682
5) Civic center 0.831
6) Apartments Office 0.822
7) Shop 0.760

As you can see they are for the most part single phase and three phase 120/240V or 120/208V commercial customers. We may need to correct on the low side beyond the meter which is on the customer side. I haven’t done this before and would like to know what can be done to address this, thanks again!

 

[stevenal]

Not sure why you'd want to put caps on the load side of the meters. How do you recover the cost? I'd keep doing what you are doing, install caps on the distribution when and where system losses, loading, and voltage drop dictate. But because these caps cost money to install and maintain, and not every load has low pf, charge the customers that do. This will also act as an incentive for customers to install and maintain their own caps.

 

[bacon4life]

Is there a minimum size customer that typically has separate demand & pf charges? I am not very familair with commercial applications, but have haven't heard of very many small businesses needing to install capacitors. Is it usually just industrial and very large large commercial applications that provide thier own pf correction?

 

[itsmoked]

I'd guess, though others will 'know', that it would likely come in about the time you have your own transformer/s for your business, since less than that, is going to be a sort of 'who dunnit'. But it will really come down to the POCO and their policies.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[apowerengr]

These loads are so small the total impact is probably less than 1200kVAr. Utilities typically don't penalize for powerfactor within their rate structure until the loads get to 200 kVA or greater.

Sure seems like any power factor correction you need should be done at the feeder level. Use VAr controllers if you have high service voltage concerns during light load conditions.

 

[tinfoil]

Our utility charges for p.f. < 90% for loads of 50kVA or greater.

 

[bacon4life]

I asked around my utility and we don't charge pf penalties below 50 kVA, and generally it is upwards of 100kVA and/or has some significant portion of motor load before we install pf metering.