Originally posted by CX
Just out of interest, how does a heatwave knock out the power supply?
Added demand from air conditioners (A/C) can:
Overload local transformers which can lead to that transformer failing.
The transformer fuses pop and depending on whether it's overhead lines or underground cables the outage can be several homes or a couple of small
Generally local transformers are sized to carry normal load during average temperatures and are quickly overloaded by high A/C demand during hot
Hot weather doesn't help the radiant cooling systems of these small pole top and underground transformers.
Stepping up a touch, the same thing can happen at the power station.
High demand from A/C usage can overload the main station transformers - although these transformers are usually more in line with what the expected
load will/can be in hot weather - and the transformer circuit breakers could trip (open) although what usually happens is that heat eventually damages
these large transformers, they fail and their circuit breakers trip.
Distribution overhead lines/underground cables can be overloaded by demand and trip on simple overload.
Along with the conductors failing if the overload is severe enough.
This last happens with old systems that use small conductors.
What was ok in the 50's doesn't cut it nowadays.
A lot of New Yorks distribution system is old - and small - stuff.
The main transmission system of a particular utility - as well as the entire transmission grid it's connected to - can lose resources due to load or
other factors such as loss of generation and lines feeding power in.
Frequency slows down and generators go off line to protect them as well as tie lines trip to protect the adjacent utilities.
Not knowing what happened in New York, at least as last reported by the news who were quoting the power company is partially true.
Minor outages have the cause determined in a short period of time even if they don't know exactly where the problem is it doesn't take too long to
The time element in this case can be a few minutes to a few hours.
Major outages, the cause is known to most everybody on the grid in a few minutes.
The problems are usually apparent and a little thinking and interpretation of data points the finger to the problem area although the exact cause may
not be known for a while.
[edit on 25-7-2006 by Desert Dawg]