How many have ringed delta?

[bobbo]

I know detroit. Anywhere else?

[reppy007]

I know detroit. Anywhere else?

Ive never heard of ringed delta...I may not understand even if you explain,but lets give it a try.Explain please.

[bobbo]

Ive never heard of ringed delta...I may not understand even if you explain,but lets give it a try.Explain please.
If wire goes down its hot. No outages anywhere. Circuit is ringed and the cans are paralleled. You have to isolate the primary on both sides and the secondary both sides to deeneegize. Sometimes you get lucky you have switches on one side and the secondary you will have a fuSed Johnny ball. You have fused can leads. They have open delta banks on different poles running the four wire. It's a great system if you are a customer. Detroit hands could tell you more.

[reppy007]

If wire goes down its hot. No outages anywhere. Circuit is ringed and the cans are paralleled. You have to isolate the primary on both sides and the secondary both sides to deeneegize. Sometimes you get lucky you have switches on one side and the secondary you will have a fuSed Johnny ball. You have fused can leads. They have open delta banks on different poles running the four wire. It's a great system if you are a customer. Detroit hands could tell you more.

Thank you,that was easy to understand,unusual but easy.Fused x-former leads.....now theres a thought.

[bobbo]

Thank you,that was easy to understand,unusual but easy.Fused x-former leads.....now theres a thought.

detroit line work : seperates real lineman from all the posers. Your brain has to work all the time! It's a great system, hot all the time. You can't fake it in detroit!

[tramp67]

Detroit has a great system for reliability. Its basically an overhead network system, transformers are paralleled and the secondaries of each transformer are fused with tattletale indicators, making it easy to spot a blown fuse. If a transformer fails, fuses on both the primary and secondary sides isolate it. I enjoy working on this system, you just need to understand it and pay attention. Being a true delta primary in a lot of the system, "the first ground is free", thus the system staying energized even with primary laying on the ground. Typical of any ungrounded delta system, with the exception that they tend to not have a normal open point on their loop systems, so no outages occur with any one failure on the system. Helps keep you from needing to go into "bad" neighborhoods after dark and minimizes outages.

[reppy007]

It does sound like a good system,but why is it only in the Detroit area?Anyway,good info about the delta system.And good to know that something is working well in the Motor-City.:D

[tramp67]

Good question, I don't know why other utilities don't have similar overhead construction. Its a good system for heavily populated areas, minimizing any outages on the system. Maybe liability? Having worked on a lot of different systems, I often wonder why utilities don't exchange information and ideas more. There's a lot of great ideas out there, but it seems like every utility feels they need to come up with their own unique ideas, good or bad.
Another interesting question, are there any other utilities besides CL&P (Connecticut Light & Power) that is going backwards, in lowering their primary voltage, building new subs and heavier lines, extra feeders to accommodate the lower voltage?

[Orgnizdlbr]

We have overhead network here in Jersey in some of our larger towns. Secondaries are fused with what we call flag fuses.

uG network tied through secondary network protectors, 4 kv and 12 kv primary with 208 sec. On UG.

240 v secondaries on OH.

[reppy007]

Since you have secondary fuses on this system ,would that mean that if one sec.leg fell down it should blow a fuse or would it have to be two or more wires down?Ive never worked with fuses on any secondary side.You mentioned that if a transformer failed,both secondary and primary fuses would blow.....I understand the primary side blowing but how would a secondary side fuse blow if the fault was on the line side of that fuse?

[tramp67]

Guessing you are referring to open wire secondary. Too high of an impedance, thus not enough current flow with secondary voltage to cause any issues with one leg on the ground. A solid phase to phase, or phase to neutral, fault on the secondary side is as likely as not to burn in the clear as to blow secondary fuses, as the transformers are all connected in parallel, thus what is considered basically unlimited available fault current. Regarding blowing both primary and secondary fuses on a transformer failure, majority of transformer faults tend to occur with the breakdown of the insulation on the primary windings. This would cause the primary side fuses to blow. But, remember that there are multiple transformers connected in parallel on the secondary side. This means the other transformers will backfeed into the secondary windings of the faulted transformer, seeing the shorted/grounded primary winding as load. They will pump as much current as possible into the faulted transformer until the fuses on the secondary side blow. And yes, the secondary fuses have indicators that show when the fuses are blown, called by different names such as flags, targets, tattletales, etc. The secondary fuses are replaceable links on a fuse block with a spring loaded indicator, generally in the range of 200 to 800 amps, depending on the kva rating of the transformer. The system really is basically an overhead network system, and any one fault will rarely cause an outage in the system. Nice to know there are other places out there with similar systems. I personally enjoy working on this type of system.

[Pootnaigle]

Umm another option is to use a huge resistor on the station transformers its connected between the neutral bushing and the earth ground and when a phase does fall the transformer sees it as load as it lays on the ground and no fault current goes back to the transformer, so no fuses blow and service is only interupted from the break on to the end of the line. Ive seen this sceneriao firsthand and it seems to work well I'm sure there must be some drawbacks or it would be more widely used . I just dunno what they are

[reppy007]

Thanks (67),good info you gave us.....but....who comes up with this $hit :D

[bobbo]

Thanks (67),good info you gave us.....but....who comes up with this $hit :D
Henry ford was the head engineer of detroit edison before he started detroit automotive works. Edison gave him the money to start the ford motor company. He had an eighth grade education. I don't know if he designed it or not. Left edison in 1903 or 1905. Super smart guy!

[Lineman North Florida]

I don't see where primary laying on the ground hot as being a good system, sounds like a death trap to me.

[bobbo]

I don't see where primary laying on the ground hot as being a good system, sounds like a death trap to me.

If you are familiar with it and know it, it's a good system. Even the customers know the system, know what to do.

guys work 19.9 in ohio and virginia likes it's no big deal, because the spread is so wide. 10 foot arm +

heard you guys go to steel monopoles and concrete, which is foreign to a lot of people.

detroit you can give people power a lot easier because you have so many options. Options that you will never get from another system. Restoring power is a breeze. And 17 lineman and trimmers have the best reputation in the US. Very few duds. They won't allow it!

[Rob]

If you are solely looking at reliability then I'd say this ringed delta may be better than a grounded wye system. But fuses are generally installed for protection, and not just to protect the system but also to protect the public. Some kid at a bus stop wouldn't understand what was laying there until it was too late.
Not looking for an argument Bobbo, just saying the system wasn't designed with safety in mind. As far as the 17 hands being top notch.... All the ones i've worked with have been!

[tramp67]

If you are solely looking at reliability then I'd say this ringed delta may be better than a grounded wye system. But fuses are generally installed for protection, and not just to protect the system but also to protect the public. Some kid at a bus stop wouldn't understand what was laying there until it was too late.!

Fuses, circuit breakers, reclosers, and such, as well as secondary breakers on csp transformers, none of these are designed or function to protect the public from electrocution. Nor is non reclose, hot line tags, or any other fast trip schemes on utility equipment. All these devices are solely for the protection of equipment from fault or overload conditions. Any utility that has a delta system can have primary laying on the ground, energized, without anything blowing or tripping. Even wye systems can have hot phases laying on the ground energized, looking completely harmless to the public. Even secondaries. Under most conditions, if a hot secondary, even bare open wire, were laying on the ground, without proper test equipment, you have no way of knowing it was energized by looking at it.
From working in Detroit, it is surprising to see how much more people in that city respect the hazard of downed lines, maybe DTE Energy does a much better job of educating joe public. The hazards of energized lines on the ground in Detroit is no different than what you would have on any other system. The biggest hazard is to linemen unfamiliar with Detroit's system, and in not understanding that simply opening a cutout or pulling the secondaries out of the transformer bushings generaly will do absolutely nothing to de-energize part of a circuit. This system is a prime example as to why the first connections to remove when changing out a transformer is the hot legs on the secondaries, as well as the last connections to make when installing a new transformer. There's always a source of backfeed, and you don't want your H1 and H2 bushings energized when making those connections.
It really is a great system, but you need to constantly pay attention to what you are doing, and it is very unforgiving if you try to take shortcuts.