4 ms·

Because you're dealing with enough power to run a city. At a minimum thousands of kV and/or Amps. If something fails, all that energy has to go somewhere...

sillysaurus 13y ago
Yes, obviously. I was prompting someone to provide more detail than that. E.g. what types of things can fail, what procedures have been put into place to mitigate the risk, examples of failures, or perhaps an interesting story or two.
- mpyne 13y ago
  At the Prototype reactor site I qualified on there was a pretty impressive tale of a student who managed to try to bring a turbogenerator onto the electrical distribution system approximately 180 degrees out-of-phase. The resultant current surge generated enough force and torque to physically lift the turbogenerator off of the deck before the breaker tripped. The amazing thing is that somehow the steam piping didn't rupture in the process. Next year the aptly-named "sync check" modification was installed to prevent shutting the circuit breaker unless the two buses had approximately equal phase.
  - smoyer 13y ago
    In the '80s, I built synchroscope controllers for Westinghouse's Nuclear Systems Division that were controlled via a main-frame computer. These were used in simulators (each reactor facility has to have a training simulator that's identical to the real control room) and were specifically used to train operators to match the phase of generators they were bringing on-line. From what I can remember, the tolerance was about +/-5% and within that range, the generators would lock to each other. If one generator was putting out AC power that was ahead of the other, the current would cause the generator to behave like a motor and speed up until it matched. The other 350 degrees of the phase dial were much more dangerous ... explosions, physical damage, etc.
- Nrsolis 13y ago
  I'll bite. I was in a gas-fired power plant when the call came in to spin up the plant turbine to meet demand. So as the turbine is spinning up, the guy misses the sync (which involves throwing a breaker when a certain light is almost extinguished; think incandescent) only to make it on the second try. At that point, the turbine goes into "follow" mode where the turbine speed is regulated to keep phase with the rest of the grid. Everything is going swimmingly until some surge causes a sudden increase in turbine speed followed by a sharp decrease. That's when the fun begins. The turbine can't spin down fast enough, which causes a phase differential, which causes a breaker to take a turbine big as a house to suddenly and violently be removed from the grid. This would normally cause an over-rev that would rip said turbine up from floor and into the air were it not for a bank of resistors that are outside that can produce a load for all that energy. When all that energy gets dumped into a bank of resistors in a switch yard on a hot summer day, you can smell it. Electricity is no joke. Respect it.
femto 13y ago
My Dad has a story on this one. He was a mechanical engineer in a Brisbane power station in the 50s/60s. In those days, generators had to be manually phase synchronised before being connected to the grid. You had to spin up the generator and vary its speed whilst monitoring the relative phase on a meter. Once the relative phase between the grid and generator was zero, it was safe to throw the switch to put the generator on-line. One day, someone threw the switch when the phase was 180 degrees... The entire generator, including its concrete foundation, ripped itself out of the ground. There was also the one about an electrician working on a generator who blasted himself with 66kV (low impedance). Massive burns, but he lived.
- femto 13y ago
  Since people liked that one, my Dad also had another good engineering disaster story, though this one is pressure related, not electricity related. He used to work for a company called James Hardie, that made asbestos cement sheeting. Part of the process involved baking the sheets in a huge autoclave, like the one pictured here [1] (note the size of the man). An autoclave is an oven, filled with high pressure steam. One day the door blew off the autoclave. The door disappeared, and the autoclave itself acted as a rocket, about the size of a shuttle solid fuel booster. It sheared off the bolts holding it to its foundation, rocketed though the back wall of the factory and ended up in a body of water about a mile away. [1] http://museumvictoria.com.au/collections/items/756810/glass-negative-vickers-ruwolt-pty-ltd-autoclave-for-james-hardie-1959 http://museumvictoria.com.au/collections/items/756810/glass-...
  - finnw 13y ago
    I wonder if the steam rocket[1] was invented as a result of an incident like this? [1] http://en.wikipedia.org/wiki/Steam_rocket http://en.wikipedia.org/wiki/Steam_rocket

sillysaurus 13y ago

Yes, obviously. I was prompting someone to provide more detail than that. E.g. what types of things can fail, what procedures have been put into place to mitigate the risk, examples of failures, or perhaps an interesting story or two.

mpyne 13y ago
At the Prototype reactor site I qualified on there was a pretty impressive tale of a student who managed to try to bring a turbogenerator onto the electrical distribution system approximately 180 degrees out-of-phase. The resultant current surge generated enough force and torque to physically lift the turbogenerator off of the deck before the breaker tripped. The amazing thing is that somehow the steam piping didn't rupture in the process. Next year the aptly-named "sync check" modification was installed to prevent shutting the circuit breaker unless the two buses had approximately equal phase.
- smoyer 13y ago
  In the '80s, I built synchroscope controllers for Westinghouse's Nuclear Systems Division that were controlled via a main-frame computer. These were used in simulators (each reactor facility has to have a training simulator that's identical to the real control room) and were specifically used to train operators to match the phase of generators they were bringing on-line. From what I can remember, the tolerance was about +/-5% and within that range, the generators would lock to each other. If one generator was putting out AC power that was ahead of the other, the current would cause the generator to behave like a motor and speed up until it matched. The other 350 degrees of the phase dial were much more dangerous ... explosions, physical damage, etc.
Nrsolis 13y ago
I'll bite. I was in a gas-fired power plant when the call came in to spin up the plant turbine to meet demand. So as the turbine is spinning up, the guy misses the sync (which involves throwing a breaker when a certain light is almost extinguished; think incandescent) only to make it on the second try. At that point, the turbine goes into "follow" mode where the turbine speed is regulated to keep phase with the rest of the grid. Everything is going swimmingly until some surge causes a sudden increase in turbine speed followed by a sharp decrease. That's when the fun begins. The turbine can't spin down fast enough, which causes a phase differential, which causes a breaker to take a turbine big as a house to suddenly and violently be removed from the grid. This would normally cause an over-rev that would rip said turbine up from floor and into the air were it not for a bank of resistors that are outside that can produce a load for all that energy. When all that energy gets dumped into a bank of resistors in a switch yard on a hot summer day, you can smell it. Electricity is no joke. Respect it.

femto 13y ago

My Dad has a story on this one. He was a mechanical engineer in a Brisbane power station in the 50s/60s. In those days, generators had to be manually phase synchronised before being connected to the grid. You had to spin up the generator and vary its speed whilst monitoring the relative phase on a meter. Once the relative phase between the grid and generator was zero, it was safe to throw the switch to put the generator on-line. One day, someone threw the switch when the phase was 180 degrees... The entire generator, including its concrete foundation, ripped itself out of the ground. There was also the one about an electrician working on a generator who blasted himself with 66kV (low impedance). Massive burns, but he lived.

femto 13y ago
Since people liked that one, my Dad also had another good engineering disaster story, though this one is pressure related, not electricity related. He used to work for a company called James Hardie, that made asbestos cement sheeting. Part of the process involved baking the sheets in a huge autoclave, like the one pictured here [1] (note the size of the man). An autoclave is an oven, filled with high pressure steam. One day the door blew off the autoclave. The door disappeared, and the autoclave itself acted as a rocket, about the size of a shuttle solid fuel booster. It sheared off the bolts holding it to its foundation, rocketed though the back wall of the factory and ended up in a body of water about a mile away. [1] http://museumvictoria.com.au/collections/items/756810/glass-negative-vickers-ruwolt-pty-ltd-autoclave-for-james-hardie-1959 http://museumvictoria.com.au/collections/items/756810/glass-...
- finnw 13y ago
  I wonder if the steam rocket[1] was invented as a result of an incident like this? [1] http://en.wikipedia.org/wiki/Steam_rocket http://en.wikipedia.org/wiki/Steam_rocket