[Electrical] Re: Looks like smart meters might act as surge protectors
That was a high voltage line coming in contact with a distribution line, likely not only fried all the meters but whatever was connected/plugged into the outlets of buildings fed from that leg. Big $$ down the drain.
Looks like smart meters might act as surge protectors
I disagree. The smart meters may not have protected anything. Here in Lake County, Florida Power is transmitted via a 230,000 Volt line from power plants on the coast. Duke Energy Substations reduce the 230,000 Volts to 68,000 Volts where it is transmitted to Sumter Electric Cooperative Substations which reduce the voltage to 14,400 volts or 7,200 volts for delivery to the distribution transformers at businesses and residences. In our distribution system if a 68,000 volt line dropped on to a 7,200 volt line the. If there was no restriction the line voltage could have reached as high as 1,000 volts at 120 volt outlets and 2,000 volts at 240 outlets for an extended period of time.
Yep, that kind of over-voltage would not be contained by a smart meter, even if it did explode (and the article said some people described its response as a "pop" and nobody said anything about the meter actually scattering its guts as shrapnel). Those over-voltages could just arc across anything that did try to open and keep the power going and going.
There's going to be much bigger problems than the meters. Electricians are going to be working overtime in that neighborhood. I hope Mr. Dumptruck had good insurance. I'll bet he didn't have enough to cover this mess.
I once witnessed a directional boring crew shoot through a secondary and then into a 4.8 kV primary. 3 houses started burning simultaneously. That boring company went out of business about 48 hours later.
Would be curious to know how power strip and/or whole house surge protectors held up to this.
Probably not well - they are designed to shunt transients to ground not absorb the energy from a constant over-voltage condition long enough to trip breakers to isolate the fault. And if the fault current is high enough to trip the breaker the gap of an open breaker may not be large enough to quench the arc so current continues to flow even with the breaker tripped.
In many ways a power cross is worse then a lightning strike: long duration and differential mode rather then common mode. Lightning strikes tend to raise the voltage on both hot and neutral, so if a device is not connected to anything else it often is able to survive undamaged.
Would be curious to know how power strip and/or whole house surge protectors held up to this.
I do not believe surge protectors would not have prevented damage caused by the surge. More likely they would have started a fire. My Brother in Law owned a commercial cleaning and fire restoration company. One of his jobs was to clean up fire damage in several rooms of a large home. The homeowner had a whole house standby generator. The generator started up due to a power failure. Almost immediately all of the power surge protectors began melting and burning. It turns out that the generators output contained enough harmonic distortion to fry the surge protectors installed to protect personal computers.
I've actually had this happen before. The voltage regulator on a standby generator went unstable due to UPSes dropping their load to the generator over and over. The voltage spikes that resulted from the oscillating voltage regulator overheated the MOVs in a power strip and burned the whole thing up (plus blew a 3 phase panel protector). I think I've posted pictures here before.
BGE had a similar incident in the county here a few years ago where some subtransmission lines crossed onto a distribution circuit. Same deal- all the appliances in the connected houses toasted.
Re: [Electrical] Looks like smart meters might act as surge protectors
About the only thing that will help with such an over-voltage condition is a means to automatically disconnect the incoming power when an over-voltage condition is detected.
Surge suppressors simply aren't designed to dissipate energy over a prolonged period of time, the components in the surge suppressor quickly overheat and burn up. They're designed to handle transients, which are often only microseconds in duration.
The automatic transfer switches for our generators at work have such a feature. Within a fraction of a second they open and disconnect power when an over-voltage condition is detected. This has actually spared equipment from expensive damages on a few occasions. Admittedly, none were quite as severe as what happened in that news article, nonetheless it is a nice added protection.
About the only thing that will help with such an over-voltage condition is a means to automatically disconnect the incoming power when an over-voltage condition is detected.
The only thing that might have saved the home electrical systems was a military spec circuit breaker I saw at a surplus store many years ago. It transferred the load to a ground bus when the breaker tripped. The biggest problem will be for customers that had their property destroyed, being attacked by various loss control weasels that will try to pay out a deprecated value for the damaged appliances rather than the replacement cost.
There's going to be a lot of Electronics and Appliances being replaced. When you see receptacle covers smoked is a good indicator.
And since we're all computer geeks here........
All the more reason to have at least some of your computer backups off-line and totally disconnected (ie. in a fireproof safe) at any one time or off-site.
Yes, that means you - Apple Time Machine fans, etc.... One good zap and there goes both your computer and your multiple Time Machine disks simultaneously. Data recovery from platters costs $1-10k depending on the breaks.
The biggest problem will be for customers that had their property destroyed, being attacked by various loss control weasels that will try to pay out a deprecated value for the damaged appliances rather than the replacement cost.
They may be weasels but that's the way it works. You are not going to get replacement cost on contents. Home is covered if you pay the replacement cost rider.
No, any equipment that can stop several hundred amps at 7.2kv+ is $$$$$$$$$. The chances of it happening are so small you're better off with just generic insurance coverage.
Re: [Electrical] Re: Looks like smart meters might act as surge protectors
Something similar happened with EPB in the 90s. The difference was there was some sort of hardware failure that allowed the higher voltage lines to fall on the lower voltage lines. An entire neighborhood had most of the appliances and other items fried. A friend that knew some people that lived in that neighborhood said that EPB told the home owners it was their problem and not EPB's. I don't know how it eventually worked out but I'm guessing at some point in time some lawyers made out well.
Re: [Electrical] Looks like smart meters might act as surge protectors
Most news reports on this story are typical media over-dramatics. The fact that the meters were "smart meters" was coincidental. With that kind of voltage surge a LOT of things went BOOM!
A few years ago a squirrel shorted a high voltage line into our neighborhood's distribution network. My whole house surge protector tripped my main breakers which saved all my appliances and electronics. Some of my neighbors were not so fortunate.
The whole house protector was rated at 13,000 joules. Much more robust than a typical power strip surge protector. Not sure it would have helped in the situation on the video, but in this day and age a $100 for a whole house surge protector is inexpensive protection.
The problem with medium and high voltage is, even when the breakers have tripped, it can still arc across the opening. The breakers are not designed for infinite voltage range, but a much more specific one. High voltage is a nasty animal. It's also really cool how the insignificant capacitance rating of a regular wire at low voltage range, become very significant at higher voltages.
10kA means that the breaker will interrupt up to a 10,000 ampere fault. This sort of rating became an issue when apartment complexes began to be fed with primary power to a step-down transformer located nearby the building. There's a code article that requires calculation of the maximum fault current and the provisions of breakers/fuses that can interrupt it.