I suspect this very dangerous

[Richard]

Probably a dumb question (since I remember very little from taking "electric shop" in high school 30+ years ago)

I'm all for safety so I'm not trying to advocate anything less than that.

That said.... don't diodes only allow electricity to flow in a single direction? Couldn't some form of diod be designed & built into all installations (or distribution panels) such that it would disallow any backfeeding?

 

[SARG]

We have a 13000 Honda generator and we backfeed using one of several HD leads I made up for both the dryer and the welder outlets.

 

[tommu56]

Probably a dumb question (since I remember very little from taking "electric shop" in high school 30+ years ago)

I'm all for safety so I'm not trying to advocate anything less than that.

That said.... don't diodes only allow electricity to flow in a single direction? Couldn't some form of diod be designed & built into all installations (or distribution panels) such that it would disallow any backfeeding?

no diodes not work current has to flow both ways on AC

 

[RonMar]

Probably a dumb question (since I remember very little from taking "electric shop" in high school 30+ years ago)

I'm all for safety so I'm not trying to advocate anything less than that.

That said.... don't diodes only allow electricity to flow in a single direction? Couldn't some form of diod be designed & built into all installations (or distribution panels) such that it would disallow any backfeeding?

yep, diodes only provide this check valve service on DC. AC flows both directions as the voltage alternates from positive to negative 60 times per second. Half of the AC waveform would be allowed to pass back down the line to the grid thru an installed diode. An installed diode would also only allow half of the AC waveform to enter the power panel...

 

[Groo]

The simplest way to do a "one way" transformer would probably be a relay. with a delay in there, and that would help with spikes on reconection too.

 

[buckeyefarmer]

happened to be talking to a neighbor the other day, and this topic came up. She said her husband once backfeed their generator to the house in an outage, and forgot to open the main breaker. Almost everything in their house got toasted when the power came back on. All I could do was think about this thread.

 

[radioman]

well, look at it this way. without a transfer switch, you just have no way of knowing you have power back on. I set mine up easily so I power only esstenails stuff, and leave light switches on for other circuit not on gen circuit. Once power comes on, I can turn off gen, saving hours on the engine.
It really nice to have a idiot proof setup for my own peace of mind for saftey on both sides, my familys and linemans.

 

[dcyrilc]

Around here, the high voltage lines are required to be hard grounded before being worked on. However, that said, human error is still possible... especially in high stress situations with long hours as in storm outage situations.

Transfer switches make the generator connection "dummy proof" to a large degree.

Even though I have backfed the electrical panel with a generator in an emergency situation, I always turn off the main breaker. I also install transfer switches on any panel which I expect to need to feed with a generator and only backfeed without a transfer switch in an emergency where power was not expected to be needed.

I'm currently in the process of moving my entire ranch over to a 45KVA gen system with automatic transfer.

I have some pictures of what happens when a person contacts live high voltage primary, but apparently stored them on a network drive at work as I wasn't able to access them remotely. If I remember on Friday when I return to work, I will post some of them. It gives a very real warning of what linemen can face if the primary is backfed.

 

[dejswa]

A lineman will always ground the line(s) or equipment he is working on (personal protective grounding - PPG) if he is going to be directly exposed to the line.

http://www.usbr.gov/power/data/fist/fist5_1/vol5_1a.pdf

 

[dmccarty]

Got curious so I googled. I found multiple references to lineman being killed by back feeding generators. I remember one death a few years ago. One reference said that at least 5 lineman were killed in 2005 due to back feeding generators.

Given that the lineman are working huge amounts of OT to restore power after a storm it is easy for them to make a mistake. How easy would it be to miss a step you have already done dozens of times in the day and think you had already done that step? When in fact you had NOT done that step at the new site. After working 10-12 hours I know I can not do any mentally demanding tasks if the work needs to be done correctly.

I have seen the lineman out in some very bad weather up in a bucket in the rain/sleet/snow/cold. Glad it is them and not me. After 12+ hours up there working they have to be mentally and physically worn out.

One of the searches I found was from a man whose neighborhood lost power. Quite a few of the houses were back feedings. When the lineman came into the neighborhood he found the back feeding houses and pulled their meters. It took weeks to get the meters back and the homeowners were fined.

Get a danged interlock and setup the panel correctly. It is cheap. It is easy. It is safer for the homeowner and the lineman. My interlock kit, 30 amp connection, and installation was around $250-300. Save your pennies if you must but do it right.

Later,
Dan