Overhead Power Lines Dangerous To Life and Property

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There is nothing that can be done that will make electrical lines perfectly reliable, especially when dealing with widespread natural disasters. But you can harden them to the more common failures that affect large numbers of customers at a time. Not going to do any real good during floods or earthquakes though.
 
paulengr said:
Yes and no. Loops are simple and reliable and you can use cheap sectionalizers on them for instance. But it only helps where loops make sense…on everything that isn’t radial or can be.

And that’s the problem. 90% of a system is customer radials. Not surprisingly 90% of the failures if not more are those same radials. In a loop system typically you have 3 fused or no fused switches. Two to isolate lines on the “loop” and a third connecting a load or feed. In a radial system you have just one. So going looped triples the cost and maintenance on switchgear to make outage recovery very rapid if one of those 10% events happen.
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What about a networked system?

https://www.reddit.com/r/Lineman/comments/ogf5n2
 
Ken_S said:
You must be in jcp&l territory
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CP&L hasn’t existed in years. Absorbed by Progress Energy then Duke. Local is Greenville Utility. Duke feeds a ton of EMCs and munis around here. Duke has their days too. When one hurricane came through there was a big enough lightning strike it actually blew a transmission line pole apart. Never seen that before.
 
Someone at a Florida utility one time gave us a demonstration on storm damage from hurricanes in areas where they had a lot of underground lines. They have a lot of ficus trees that have extremely extensive route systems and tend to do a lot of damage to underground cabling when they fall over. So in addition to undergrounding you might have to cut down trees within a very large right of way area for the cable, which is definitely not popular nowadays. I think there’s also issues with power factor that would need to be overcome, if there’s excessive amounts of underground cables. Also there’s the fact that even though consumers may act like they want it in reality most of them probably aren’t willing to pay the cost of not only maintaining but transitioning everything to underground
 
mbrooke said:
What about a networked system?

https://www.reddit.com/r/Lineman/comments/ogf5n2
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Again you aren’t going to be feeding double wide trailers from an RMU as your POD. In terms of total line length, poles, etc., 90% or more of any POCO are radials. All those small 130 V residential transformers and their associated radials vastly exceed the distribution system feeding them.

I’m not denigrating network or at least looped distribution lines. And obviously radial distribution has the possibility of affecting large numbers of customers. What I’m pointing out is the large number of customers that have to be addressed one by one after storm damage.
 
paulengr said:
Again you aren’t going to be feeding double wide trailers from an RMU as your POD. In terms of total line length, poles, etc., 90% or more of any POCO are radials. All those small 130 V residential transformers and their associated radials vastly exceed the distribution system feeding them.

I’m not denigrating network or at least looped distribution lines. And obviously radial distribution has the possibility of affecting large numbers of customers. What I’m pointing out is the large number of customers that have to be addressed one by one after storm damage.
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Ok, so I got a concept pic drawn up:

https://imgur.com/MQtyyHg

https://imgur.com/aO1dPO4
 
paulengr said:
Again you aren’t going to be feeding double wide trailers from an RMU as your POD. In terms of total line length, poles, etc., 90% or more of any POCO are radials. All those small 130 V residential transformers and their associated radials vastly exceed the distribution system feeding them.

I’m not denigrating network or at least looped distribution lines. And obviously radial distribution has the possibility of affecting large numbers of customers. What I’m pointing out is the large number of customers that have to be addressed one by one after storm damage.
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Basically I have 3 MV schemes pictured.

1. Is a 5 feeder spot network system capable of operating under N-2. Each spot network has 5 transformers with the secondaries paralleled into a collector bus- 120/208, 240/416 and 277/480 would radiate out, fused or with limiters. The trafos can either be in an above ground structure or in an underground vault. The MV is segmented into sections with switches (midpoint switches normally open) so either manual or automatic forced load transfer to other subs can take place for extreme contingencies.

2. A 300-400 amp parallel normally open loop with breakers and sensationalizing switches. The breaker or motorized switch are in a kiosk or pad style station feeding a single trafo that can be anywhere from 30 to 1000kva in size. The LV radiates out to customers. A loop scheme type approach is used where breakers open for a fault, switches sub sectionalize around the fault cable during the dead time, and then a normally open breaker closes back in to pickup the healthy segments. No customers are lost for a single feeder fault.

3. A 600 amp trunk line that daisy chains through PME padmount gear with 200E fuses protecting 200 amp sub loops. The 600 amp switches may or may not be automatic, though preferably automatic as part of a loop or source transfer (dual source). The 200 amp sub loops daisy chain through an unlimited number of padmounts, single phase or 3 phase. A fault on the sub loop blows a PME fuse, however, line crews can located the fault cable, and manually switch it out via loop switches in each padmount restoring service while the cable can be thumped and repaired.


These are the onl6 3 approaches coming to mind that balance cost and reliability.
 
paulengr said:
CP&L hasn’t existed in years. Absorbed by Progress Energy then Duke. Local is Greenville Utility. Duke feeds a ton of EMCs and munis around here. Duke has their days too. When one hurricane came through there was a big enough lightning strike it actually blew a transmission line pole apart. Never seen that before.
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JCP&L…

Jersey Central Power and Light.
 
paulengr said:
Again you aren’t going to be feeding double wide trailers from an RMU as your POD. In terms of total line length, poles, etc., 90% or more of any POCO are radials. All those small 130 V residential transformers and their associated radials vastly exceed the distribution system feeding them.

I’m not denigrating network or at least looped distribution lines. And obviously radial distribution has the possibility of affecting large numbers of customers. What I’m pointing out is the large number of customers that have to be addressed one by one after storm damage.
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For the EHV I have 5-7 parallel cables, cross bonded sheathes connecting the generating stations to the interconnecting subs. 5-6 autos, 250-400MVA auto transformers. Variable shunt reactors to offset the cable charging current.

For the HV I have 5-2 parallel cables, 4-5 trafos in the area subs, 20-50MVA, reactors for compensation as needed.
 
mbrooke said:
For the EHV I have 5-7 parallel cables, cross bonded sheathes connecting the generating stations to the interconnecting subs. 5-6 autos, 250-400MVA auto transformers. Variable shunt reactors to offset the cable charging current.

For the HV I have 5-2 parallel cables, 4-5 trafos in the area subs, 20-50MVA, reactors for compensation as needed.
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Ok so would you run 5-7 parallel cables per phase to a customer, particularly with at least two separate feeders?
 
paulengr said:
Ok so would you run 5-7 parallel cables per phase to a customer, particularly with at least two separate feeders?
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If voltage drop, ground fault loop impedance, or steady state current draw required it then yes. No different then running parellel sets for a 4000 amp service as done with the NEC.
 
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