Power transmission question???

pmanton

pmanton

Final Approach
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Why do I see what look like power factor correction capacitors on a power pole out in the middle of nowhere? I associate PF correction with an industrial environment with a lot of inductive motors & such.
 
pmanton said:
Why do I see what look like power factor correction capacitors on a power pole out in the middle of nowhere? I associate PF correction with an industrial environment with a lot of inductive motors & such.
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Long transmission lines, particularly if they are lightly loaded, can incur inductive loads.
 
 
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coloradobluesky said:
Those cylindrical cans are actually usually transformers. They look like this:
https://www.google.com/search?q=power+line+transformers&biw=1093&bih=530&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjP6t3R9rzQAhXHllQKHVfwB6YQ_AUIBygC#imgrc=KJlbuS2MuKznAM:

Although it is true that there can be capacitors up there too. They usually look like this:
https://www.google.com/search?q=power+line+capacitors&biw=1093&bih=530&source=lnms&tbm=isch&sa=X&ved=0ahUKEwit-4GG97zQAhUhxFQKHQHRDwoQ_AUIBygC#imgdii=hp7KeNdhgV0b2M:;hp7KeNdhgV0b2M:;387kEuV_qUx27M:&imgrc=hp7KeNdhgV0b2M:

Power line components look different than discrete circuit board components.
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AKA Pole Pigs for the transformers. For sure high voltage components look a lot different than garden variety items that perform the same function.
For example, this is a circuit breaker: http://ittehad-electric.com/index.php/products/meters/high-voltage-circuit-breakers Usually not found on
poles, though.

Dave
 
pmanton said:
Why do I see what look like power factor correction capacitors on a power pole out in the middle of nowhere? I associate PF correction with an industrial environment with a lot of inductive motors & such.
Click to expand...
You sure they're capacitors? They're normally rectangular in shape and connected across the phases with relatively small gauge wires along with fuses and disconnects. Anything round is likely to be voltage compensation, or switchgear (e.g. sectorizers). If they are caps there's the a good chance that rural loads include a lot of motors if there are certain kinds of farm operations.
 
I see caps on power lines all the time in my area, North Texas.
 
Sac Arrow said:
Long transmission lines, particularly if they are lightly loaded, can incur inductive loads.
Click to expand...

This is the correct answer.

I recently completed the construction of a relatively small powerline. 69,000 volt line that ran approx. 20 miles. We required power factor correction at the end of the line to provide proper VAR support to prevent voltage drops. Our main problem was inductive load but the line itself does contribute to the inductive load. The other benefit is that as your power factor gets better (closer to 1), the current needed decreases as you aren't having to send those VARs down the line and your I2R losses decrease.


Qualifications: Electrical Engineer/Project Manager who builds powerlines & substations amongst other things.
 
I don't know much about power line design, construction or operation. I did have to deal with about 20 miles of 43.5kv line out in the boonies for about five years. There were voltage correction transformers every 5 miles or so. Not many capacitors at all. Certainly we didn't put any capacitors on our system. I don't recall the exact power factor in our billing but that just means it was darn close to 1 or I would have been looking for ways to fix it.
 
Long transmission lines, particularly if they are lightly loaded, can incur inductive loads.
Thanks you have increased my knowledge :) I am in awe of the expertise of the members of this group.
Ask any question and someone will know the answer.
 
I'm not an EE myself but I work closely with them.
 
Clark1961 said:
I don't know much about power line design, construction or operation. I did have to deal with about 20 miles of 43.5kv line out in the boonies for about five years. There were voltage correction transformers every 5 miles or so. Not many capacitors at all. Certainly we didn't put any capacitors on our system. I don't recall the exact power factor in our billing but that just means it was darn close to 1 or I would have been looking for ways to fix it.
Click to expand...

I wonder about those voltage correction transformers. Wouldn"t it make more sense to correct the voltage in one step at the substation rather than having several sources of problems along the way? Is it that much less efficient to run the line at a couple percent lower voltage?
 
There's a sweet spot in power distribution voltage. The higher the voltage, the more power that can be delivered for a given resistive loss. However, higher voltages have their own losses (try standing under a high tension power line with a fluorescent tube). Sort of like induced and parasitic drag.
 
They aren't used in the US much but some long, high voltage transmission lines are DC (HVDC) in order to avoid the inductive losses of an AC line.
 
Sac Arrow said:
They aren't used in the US much but some long, high voltage transmission lines are DC (HVDC) in order to avoid the inductive losses of an AC line.
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Also gets around having to having the line frequency synchronized.
 
weilke said:
I wonder about those voltage correction transformers. Wouldn"t it make more sense to correct the voltage in one step at the substation rather than having several sources of problems along the way? Is it that much less efficient to run the line at a couple percent lower voltage?
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I think they design the line to deliver nominal voltage at any point on the line. Voltage changes at intermediate take points could cause problems. We did have to change the taps on our transformers from time to time.
 
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