The company that I work for has developed an instrument that monitors low voltage (120/240) power lines that are "t-tapped." The only residential neigborhoods that use this type of technology (or lack thereof) is overseas (that we know of.) We have been traveling to the UK to test our equipment. In a typical neighborhood they have one transformer with 4 or 5 3-phase cables running down different areas. Each house is then tapped off of the main line and then buried underground. Obviously not the best way to run electrical but hey, if gives us something to do. We are obviously looking for a place in the states that is set up like this. We have recently found out that some places in South America also distribute power this way. Any information that you know would be appreciated! Thanks
Multiple houses "T-tapped" off of one X-Former
- Thread starter bcampell4
- Start date
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bphgravity
Senior Member
- Location
- Florida
Re: Multiple houses "T-tapped" off of one X-Former
It is my understanding that certain areas of Baltimore are connected in this manner, if I am understanding you desrciption properly.
It is my understanding that certain areas of Baltimore are connected in this manner, if I am understanding you desrciption properly.
charlie
Senior Member
- Location
- Indianapolis
Re: Multiple houses "T-tapped" off of one X-Former
I think you will find that type of distribution in your own back yard. Electric utilities have been installing a single transformer to serve multiple customers for years. We run secondary (overhead and underground) from pole to pole or from pedestal to pedestal and then tap off from there to individual homes and to feed street lights.
I think you will find that type of distribution in your own back yard. Electric utilities have been installing a single transformer to serve multiple customers for years. We run secondary (overhead and underground) from pole to pole or from pedestal to pedestal and then tap off from there to individual homes and to feed street lights.
charlie
Senior Member
- Location
- Indianapolis
Re: Multiple houses "T-tapped" off of one X-Former
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- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Re: Multiple houses "T-tapped" off of one X-Former
I can only believe this if you mean the transformers at the substations (i.e., not the ones on the poles in the alleys).
Re: Multiple houses "T-tapped" off of one X-Former
The type of system that they use is all underground. They have a substation (they call transformer) and then from there they have anywhere from 1 to 8 cables (3 phase) coming off of the transformer, each phase individually fused. There is no power above ground except were the have "link boxes" installed to help trace the faults i.e. cutting the cables in half to trace it out. They lay the cable in a trench (usually only about 12 to 18 inches deep) and when a house is present, they dig up the cable, put a splice in it (tap on with a single conductor to one of the phases) and then wrap a "band-aid" around it and bury it. they have these all over the place and they are causing arcing and phase-to-ground faults. The usual cable that they use is aluminum with an oil-soaked paper insulator and then the conductors are then surrounded with a sheild (nuetral conductors) and then the overall sheath is a lead-based covering. It is really hard to take that this is the way that they distribute power. But hopefully that explains it a little better.
The type of system that they use is all underground. They have a substation (they call transformer) and then from there they have anywhere from 1 to 8 cables (3 phase) coming off of the transformer, each phase individually fused. There is no power above ground except were the have "link boxes" installed to help trace the faults i.e. cutting the cables in half to trace it out. They lay the cable in a trench (usually only about 12 to 18 inches deep) and when a house is present, they dig up the cable, put a splice in it (tap on with a single conductor to one of the phases) and then wrap a "band-aid" around it and bury it. they have these all over the place and they are causing arcing and phase-to-ground faults. The usual cable that they use is aluminum with an oil-soaked paper insulator and then the conductors are then surrounded with a sheild (nuetral conductors) and then the overall sheath is a lead-based covering. It is really hard to take that this is the way that they distribute power. But hopefully that explains it a little better.
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
Re: Multiple houses "T-tapped" off of one X-Former
In my area, there is a history of high end dwellings going in on a "private secondary". The age of the two neighborhoods that I have worked on dates to development in the late Teens and Twenty's. A single transformer, pole mounted, 120/240 V 1 ? secondary was as much as half a block away, hidden behind "lesser" houses.
In the two neighborhoods I am familiar with, 6 to 8 homes were supplied from a lead sheathed service lateral. As homes were added, they would be teed off the lateral laid along the right-of-way.
As loading increased, more problems occurred. I know for a fact that one of the old laterals has been retired. I suspect that the PoCo will have several more of these "private secondary" installations that they have inherited with the passage of time.
In my area, there is a history of high end dwellings going in on a "private secondary". The age of the two neighborhoods that I have worked on dates to development in the late Teens and Twenty's. A single transformer, pole mounted, 120/240 V 1 ? secondary was as much as half a block away, hidden behind "lesser" houses.
In the two neighborhoods I am familiar with, 6 to 8 homes were supplied from a lead sheathed service lateral. As homes were added, they would be teed off the lateral laid along the right-of-way.
As loading increased, more problems occurred. I know for a fact that one of the old laterals has been retired. I suspect that the PoCo will have several more of these "private secondary" installations that they have inherited with the passage of time.
charlie
Senior Member
- Location
- Indianapolis
Re: Multiple houses "T-tapped" off of one X-Former
Interesting, I have never heard of that type of installation. The cable you are talking about is PILC (paper insulated, lead covered) and has been removed from the NEC. It is still alive and well though since it is the only type of cable that really holds up well when it is run next to steam lines in our downtown network. We still use it for 600 V and 13.2 kV installations.
Interesting, I have never heard of that type of installation. The cable you are talking about is PILC (paper insulated, lead covered) and has been removed from the NEC. It is still alive and well though since it is the only type of cable that really holds up well when it is run next to steam lines in our downtown network. We still use it for 600 V and 13.2 kV installations.
Re: Multiple houses "T-tapped" off of one X-Former
The type of neigborhood has a transformer, and then a 3 or 4 conductor cable (different phases) and will be routed usually along the street underground. Every third house should be on the same phase as they try to alternate phases to even out the phases. An example of the cable they use can be seen here:
http://www.africancables.com/products.html
The type of neigborhood has a transformer, and then a 3 or 4 conductor cable (different phases) and will be routed usually along the street underground. Every third house should be on the same phase as they try to alternate phases to even out the phases. An example of the cable they use can be seen here:
http://www.africancables.com/products.html
Re: Multiple houses "T-tapped" off of one X-Former
bcampell4
I recently spoke to one of the engineers in England and they use 500 to 1500 kva transformers
with a bunch of secondary runs.
[ December 29, 2005, 11:59 AM: Message edited by: bob ]
bcampell4
What do you mean by "t-tapped "? As Charlie says the utilities here run secondary an tap 3 or 4 customers at the end of the run. Why can not you equipment be used here? Many of the older sections of a town have old copper secondary with 25 customers on a transformer. These usually will have overloads and low voltage. The circuits are eventually corrected.
I recently spoke to one of the engineers in England and they use 500 to 1500 kva transformers
with a bunch of secondary runs.
[ December 29, 2005, 11:59 AM: Message edited by: bob ]
Re: Multiple houses "T-tapped" off of one X-Former
When I say "T-tapped" I am meaning that (for example, a new house is built)they dig up the 3 phase cable, "tap" into one phase of the cable with another single conductor cable that runs to the house. On this site, they show the "joint" that they use to do this.
http://www.jointingtech.co.uk/products/table.asp?cat=4
When I say "T-tapped" I am meaning that (for example, a new house is built)they dig up the 3 phase cable, "tap" into one phase of the cable with another single conductor cable that runs to the house. On this site, they show the "joint" that they use to do this.
http://www.jointingtech.co.uk/products/table.asp?cat=4
Re: Multiple houses "T-tapped" off of one X-Former
What our instrument does is monitors the cable (between two instruments) and tells you where the fault is (if it occurs between the two instruments). It could be used here in the US, but being that the service cables are usually no more than 50-100 ft long, and above ground, it is easy to see/fix the problem, therefore monitoring the cable wouldn't be needed.
If there is a problem (short or open) on the network in the US, only one or a few houses are affected. If there is a short/open on the network in the UK, many houses are affected.
What town/towns are these? Is the cable routed underground and what are the distances between each house?
What our instrument does is monitors the cable (between two instruments) and tells you where the fault is (if it occurs between the two instruments). It could be used here in the US, but being that the service cables are usually no more than 50-100 ft long, and above ground, it is easy to see/fix the problem, therefore monitoring the cable wouldn't be needed.
If there is a problem (short or open) on the network in the US, only one or a few houses are affected. If there is a short/open on the network in the UK, many houses are affected.
Re: Multiple houses "T-tapped" off of one X-Former
Here is a rough drawing of a short cable coming from a transformer.
H is a house
! is the single conductor
-- is the main 3or4 conductor cable
o is the joint/tap to the main cable
(all conductors/splices are underground)
_____________H____H_______H______H_______H
_____________!_____!_______!_______!_______!
_____________!_____!_______!_______!_______!
_____________!_____!_______!_______!_______!
X-former ------o-----o-o------o-o-----o-----o--o--o
_____________!_______!_______!_____!_____!_____!
_____________!_______!_______!_____!_____!_____!
_____________!_______!_______!_____!_____!_____!
_____________H______H_______H____H_____H____H
[ December 29, 2005, 02:57 PM: Message edited by: bcampell4 ]
Here is a rough drawing of a short cable coming from a transformer.
H is a house
! is the single conductor
-- is the main 3or4 conductor cable
o is the joint/tap to the main cable
(all conductors/splices are underground)
_____________H____H_______H______H_______H
_____________!_____!_______!_______!_______!
_____________!_____!_______!_______!_______!
_____________!_____!_______!_______!_______!
X-former ------o-----o-o------o-o-----o-----o--o--o
_____________!_______!_______!_____!_____!_____!
_____________!_______!_______!_____!_____!_____!
_____________!_______!_______!_____!_____!_____!
_____________H______H_______H____H_____H____H
[ December 29, 2005, 02:57 PM: Message edited by: bcampell4 ]
Re: Multiple houses "T-tapped" off of one X-Former
You origional post spoke of monitoring low voltage.
Finding a fault is a different problem. I would agree that here the underground cables are not long. However utilities sometimes install fault locators on the primary cable.
ty
Senior Member
- Location
- 3rd Rock from the Sun
Re: Multiple houses "T-tapped" off of one X-Former
out of curiosity, how many (or what percentage) of you crew can splice it when need be???
Hey Charlie,Originally posted by charlie:
Interesting, I have never heard of that type of installation. The cable you are talking about is PILC (paper insulated, lead covered) and has been removed from the NEC. It is still alive and well though since it is the only type of cable that really holds up well when it is run next to steam lines in our downtown network. We still use it for 600 V and 13.2 kV installations.
out of curiosity, how many (or what percentage) of you crew can splice it when need be???
beanland
Senior Member
- Location
- Vancouver, WA
Re: Multiple houses "T-tapped" off of one X-Former
We often install something akin to this in Palo Alto CA. 120/240V secondary under the sidewalk with taps to individual homes. In some cases it is 3-phase 120/208V with network (3-wire 120/208V taps to homes. Rather than a home run from house to transformer, service laterals tapped from a secondary system are cheaper.
We often install something akin to this in Palo Alto CA. 120/240V secondary under the sidewalk with taps to individual homes. In some cases it is 3-phase 120/208V with network (3-wire 120/208V taps to homes. Rather than a home run from house to transformer, service laterals tapped from a secondary system are cheaper.
charlie
Senior Member
- Location
- Indianapolis
Re: Multiple houses "T-tapped" off of one X-Former
Todd, we have several cable splicers in the downtown central business district that can handle this type of splice. It is not as difficult now that splice manufacturers have kits to do the splicing with. They used to have to pound and wipe the splice jacket to form the lead sleeve over the finished splice.
Todd, we have several cable splicers in the downtown central business district that can handle this type of splice. It is not as difficult now that splice manufacturers have kits to do the splicing with. They used to have to pound and wipe the splice jacket to form the lead sleeve over the finished splice.
LawnGuyLandSparky
Senior Member
Re: Multiple houses "T-tapped" off of one X-Former
What is the voltage of these underground cables in Africa? The website rates them at 500-6.6kv.
What is the voltage of these underground cables in Africa? The website rates them at 500-6.6kv.
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