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An estimated 60 to 80 fires, 3 explosions, and numerous gas leaks were reported last night in the towns around Lawrence, MA (north of Boston). The incident has been linked to lines operated by Columbia Gas of Massachusetts. Columbia Gas has not released an official cause yet, but MEMA (The Massachusetts Emergency Management Agency) and some of the local firefighters have speculated that the cause was an over-pressurized gas line. Columbia was conducting planned upgrades on the lines at the time of the incident. One person has been killed; 25 more have been injured.
I was listening to the fire radio as it happened and it sounded like complete chaos -- it was just the dispatch, but there was not a single moment of silence as they scrambled to get crews to all of the affected areas and coordinate the response across four separate towns (Lawrence, Andover, North Andover, and Methuen.) The local first responders were initially asking residents to shut off their gas lines; this quickly changed to calls for all Columbia Gas customers to evacuate, which then increased to an order for immediate evacuation of the entire area. Overnight police and fire officials were going door-to-door enforcing the evacuation, and it is not known at this time when residents may be allowed to return. The electric service has been shut down to the entire area to limit possible sources of ignition, and officials have stated there are over 8000 homes which need to be individually inspected before the residents can return.
So far, Columbia Gas has not provided any confirmation or explanation of the exact cause of this disaster...but I'm sure we've got some people here who have some speculation to offer...
The local Eagle Tribune has a number of articles with further information, and there's limited coverage in national sources like CNN.
(Score: 2) by jmorris on Friday September 14 2018, @11:30PM (4 children)
You mean old switching power supplies without PFC (Power Factor Correction) features. Now it is only really crappy low end products that cause problems. Too bad most of the marketplace is filled with cheap crappy Chinese junk.
(Score: 2) by hendrikboom on Saturday September 15 2018, @08:04AM (3 children)
Can someone explain to me what switching and nonswitching power supplies are and how they work and differ? They've been mentioned off and on here, and I haven't been able to find an explanation..
(Score: 2) by shortscreen on Saturday September 15 2018, @09:42AM
The big plastic bricks that used to come with the Atari and Commodore contained a transformer to turn 120VAC into a lesser AC voltage, followed by a rectifier/regulator to turn it into 5VDC. These things were not very efficient and only put out 10W or so. A switching power supply is more complicated, but more efficient. Instead of controlling the output voltage by dissipating the excess as waste heat, it feeds a high frequency into a big capacitor and varies the duty cycle to maintain the charge. It's like trying to keep your speedometer at 60mph but instead of holding the accelerator pedal steady you repeatedly floor it and then let off, 100,000 times per second.
(Score: 0) by Anonymous Coward on Saturday September 15 2018, @12:36PM
A linear or regulated power supply uses a transformer to downscale/upscale the voltage from AC input to the required output voltage followed by a rectifier to convert to DC, then gets out of the way to let the rest of the system (the power line and equipment) handle the power transfer. Any mismatch in supply and demand (power transfer is fast, but not instantaneous) is immediately dissipated as heat. A switched-mode power supply has the rectifier first, then generates its own AC signal at around 100kHz or higher, and feeds that into a transformer. Because of the much higher frequency, the transformer can be much smaller, and because of the more intelligent circuitry, the power draw can be much better controlled resulting in less heat dissipation.
Wikipedia [wikipedia.org] has its own explanation and comparison:
(Score: 2) by VLM on Monday September 17 2018, @01:46PM
Totally unfair not to provide an automobile analogy
Linear supplies control yer car speed VERY roughly using the transformer/holding down the accelerator to some angle and locking it at X percent output. Then fine tune the speed by pressing on the brakes generating some amount of heat depending on load (uphill? downhill?) and depending on input voltage (held the accelerator down too much or too little?) Its actually a bad analogy because the accelerator controls power but transformers actually control voltage which when multiplied by current gives you power.
Switchers work like a crazy person either foot to the floor or put it in neutral and coast. Which is hard on the mechanical parts but is a fairly reasonable way to run a switching power supply or air compressor or home HVAC furnace if they're engineered to do it. The reason why you'd do it is the energy cost when its in neutral is zero (assuming engine cut off completely not merely idling) and the efficiency of engines -n- stuff is usually designed to be maximum at full power for handwavy reasons so on average the efficiency is roughly the theoretical max of the engine despite the fact you might only average 25 mph not whatever flooring it eventually approaches.
Or even shorter but worse analogy is linear is like old person controlling speed by riding the brake whereas switcher is kinda like controlling speed by heavily manipulating a hybrid car system.