|
North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Cascading Failures Could Crash the Global Internet
On Thu, 6 Feb 2003, N. Richard Solis wrote: > The main cause of AC disruption is a power plant getting out of phase > with the rest of the power plants on the grid. This is typically a result of sudden load change (loss of transmission line, short, etc) changing the electromagnetic drag in generators, and, therefore, the speed of rotation of turbines. > When that happens, the plant "trips" of goes off-line to protect the > entire grid. Some difference in phase is tolerable, the resulting cross-currents generate heat in the trasmission lines and transformers. It is not sufficient to disconnect a generator from the grid. Since water gates or steam supply can not be closed off fast, the unloaded turbine would accelerate to the point of very violent self-destruction. So the generators are connected to the resistive load to dump the energy there. Those resistors are huge, and go red-hot in seconds. If a gate or valve gets stuck, they melt down, with the resulting explosion of the turbine. > You lose some generating capacity but you dont fry everything on the > network either. Well... not that simple. A plant going off-line causes sudden load redistribution in the network, potentially causing overload and phase shifting in other plants, etc. A cascading failure, in other words. --vadim
|