60 hz as a time standard [telecom]

At some point in the 1930s or shortly later, the commercial power

> grid became reliable enough to use the 60 Hz as a means to run > clocks accurately. This led to the loss of pendulum regulator > clocks and Western Union time signals

Many decades ago my Uncle was a district manager for PG&E, and one of the perks was a cabin at a turn-of-the-century hydrogenerating facility that had been automated a long time ago. His cabin was the plant manager's cabin originally, and in the living room was this neat clock. It was a tall grandfather clock affair, with a temperature-compensated pendulum to keep it accurate. It had one large dial with a smaller one inset in it. The smaller one was a conventional clock face; the big dial had a single hand that read zero straight up and plus and minus seconds on either side. The mechanism had two clock drives, the pendulum one and an electric one driven by the power station generator output, and the big hand kept track of how far the frequency from the generator had drifted. I never saw it read anything other than zero, but it wasn't hard to imagine that in the manually controlled days a glance at that clock might have resulted in a phone call to the plant operator to get the fequency back on track.

Marty

Reply to
Martin Bose
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I believe they key here is "the grid". AFAIK in any power grid each supply generator connecting to it has to exactly match phase otherwise the consequences are (apparently) not good at all.

It is my understanding that once connected the grid itself keeps all the AC generators in sync through the overall reflected load coming back down the line.

** Moderator note:

If a generator is out-of-phase, power flows _from_ the grid, _into_ the generator, to speed-up (or slow down) the moving parts until the phases do match. That energy flow into the generator is ultimately dissapated as excess heat from the machinery. It can be a *lot* of heat, depending on how fast the hardware can adapt to the phase error. Generation facilities do run monitoring equipment to check the phase of the external plant against that of the generators; which which will then adjust the speed of the prime mover powering the generator, to ensure maximum efficiency, and minimal thermal losses.

There is a story told in power-generation circless about an occasion (now more than half-a-century ago) when somebody brought a multi-megawatt generator "on line" exactly _180_degrees_ out-of-phase with the grid. Before the overload cutouts could act, the generator (and the unit feeding it) was a pile of smoking rubble, had torn itself loose from its mountings, and moved several _feet_. Amazingly, no one was killed.

Reply to
David Clayton

Heh!

If you want to see a 9-second video of a very high voltage switch failure:

I've had that video on my website since 2003 and I seem to be the only person on the planet who has a description of what it is we're seeing in that video accompanying the video itself; none of the multiple copies of that video on YouTube have a description. Here are the aggregated descriptions I saved in a single file:

The original author's page doesn't have a valid link to the video anymore.

Reply to
Thad Floryan

I once did a story on the power dispatchers for Oklahoma Gas & Electric Company, the electric company that serves much of Oklahoma and western Arkansas. This was probably in the 19550s.

They had two clocks, one showing the grid frequency and the other the local frequency of their power plants. The also had a pen register showing frequencies of the grid, and showed me where earlier that day the frequency on the grid slipped below 60 Hz, a signal for all the other operators to add to their share of the load to bring the frequency back up.

They told me that there was a fire at a generating plant in Cleveland which caused them to drop their load and the frequency to drop until other plants across the country could pick up the load, and the frequency on the grid was back up to 60 Hz within a few minutes. As I recall, the frequency went above 60 HZ briefly to bring the clocks back to standard time.

I read in the evening paper (remember those?) a story about the fire in Cleveland. The drop in frequency drop was only to 59.9 or something like that.

Wes Leatherock snipped-for-privacy@yahoo.com snipped-for-privacy@aol.com

Reply to
Wes Leatherock

Tom Van Baak, amateur metrologist, made measurements of his local utility power and found that (over the course of the two months he studied) the frequency varied from 59.950 Hz to 60.050 Hz. See .

-GAWollman

Reply to
Garrett Wollman

ISTR reading about a plan at one time to alter the line frequency as a method of sending an alert for emergencies, similar to the EBS now in place.

Anyone remember anything about this?

Jon

** Moderator Note: This strikes me as 'unlikely', to put it charitably.

It would either have to be an alert for a -large- part of the country -- the entire area served by one of the less-than-half-dozen utility 'grids', with precise coordination among _all_ the electric generation facilities therein,

*OR* each electic utility in the affected area would have to _disconnect_ from the 'grid', adjust their generator frequency to generate the trigger signal, then re-phase with the 'grid' and reconnect to the grid. One does not -- one *cannot* -- make an abrupt change to the frequency on an A.C. power distribution system. _Every_ motor, generator, alternator, and ferro- resonant transformer on that distribution system will resist the change. This puts a non-trivial lower limit on the time it takes to send a signal by this method.

Second, to _detect_ the change in the power-line frequency, you have to have a 'more stable' reference to compare against.

Third, there is the 'minor matter' of *who* would/could _require_ all the various electric utilities to install, maintain, and operate the additional gear required to make this work. Electric utilities are not licensed and regulated to anywhere near the degree that RF transmitters are. There is little Federal oversight -- most regulation is at the level of state Public Utilities Commissions, an/or local 'franchise' oversight.

The FCC, by virtue of setting terms for license issuance, can require any/all transmitter operators to a)maintain emergency signal receivers, b) broadcast emergency signals, and even to c) shut down on government command (a la the old CONELRAD).

I don't know of any agency with similar authority over electrical generation and distribution facilities. The 'grid' is, to the best of my knowledge, effectively _unregulated_ being simply a co-operative venture of the participating electric utilities, in their own self-interest.

Reply to
Jon Danniken

You probably saw an episode of the PBS series "History Detectives". The plan was not to alter the power line frequency, but to superimpose an RF signal on the line that would activate an alarm that was plugged into a household outlet. The device worked, but the plan did not, as the alert carried no information about what to do when the alarm went off.

-GAWollman

Reply to
Garrett Wollman
[snippeth]

These were also planned for specialized local use, such as around the (NYC suburban) Indian Point nuclear power plant. These would have alerted people to basically turn on their radios...

- which, since this would be the electrical company sending out the warning, would kind of work.

I remember seeing stories about them. Don't know if any were actually put into use.

Reply to
danny burstein

I think I came across it in an old mail order catalog that supplied kits to hobbyists, but you're probably right about it being an RF signal instead of the timebase (it's been awhile).

I always thought it sounded like a neat idea, since not everyone has a TV or radio turned on, but there is always an outlet to plug something into. Speaking of which, I wonder if it was ever considered to include the internet (which would probably now include smart phones) on the EBS.

Jon

Reply to
Jon Danniken

Back in the 1960s we had civil defense training which included what to do if the air raid sirens went off. Everyone had instruction cards. IIRC, there were two types of signals. Radios made at the time had a little triangle at two parts where we were supposed to tune to get instructions. We were not to use the telephone.

Every Wednesday at noon for decades the city would sound the sirens briefly as a test.

I have no idea if the sirens still exist or are tested, or when they were discontinued. I suspect that the demise of the Soviet Union and the end of the cold-war inspired the demise of the old civil defense program, as well as an aging system. (This would include the old fallout shelters with their cans of water and crackers. Our building repainted the cans to use as paper recycling drums.)

As an aside, the loud siren atop the local volunteer firehouse was replaced some years ago with an electronic siren. I think the firefighters have beepers now.

ob telephone: Small town telephone directories would list the firechief's home number as the number to call in case of fire.

Reply to
HAncock4

This brings back several memories. Our small town had a light bulb hung across the main street that served as the "cop light." The bulb was connected to a switch inside the 2nd-floor manual central office. When a call came in to the operator for the police, if they were unable to find the cop, they'd turn on the light, and the cop would call in for the message. After the CO was automated, the light was triggered by a call to an answering machine. The volunteer fire department was called by a siren on a pole (it doubled as the air raid siren, with a different warble). When a person called the fire department number, the siren would sound until the call was answered on one of several "fire phones" located in the homes of several fire department members (and in the fire house). They would take the call, go to the fire house, and write the call location on a blackboard before taking out one of the fire trucks with the people who had arrived. Latecomers would take out a second truck when they got there.

Many of the old air raid sirens are still there, I believe. I think many of them double for use as hurricane or tsunami warning sirens.

Daryl Gibson

Reply to
daryl.gibson

It worked? Surely an RF signal would not pass a transformer designed to work optimally around 60 Hz? Or should "RF" be interpreted liberally here?

Reply to
Geoffrey Welsh

Some of it does, due to interwinding capacitance between the primary and secondary. It is also possible to put shunt caps around the transformer to make it easier to pass the signals (or active repeaters).

The same concept is being promoted today as BPL, although the BPL people are trying to get far more bandwidth at far higher frequencies (with pretty awful RFI consequences).

Carrier current transmissions, though, are still very popular for low bandwidth low frequency RF applications, and the power companies often use them for carrying signalling data.

--scott

Reply to
Scott Dorsey

A side note on 60Hz...

I just got a Obitalk ATA, a TCP/IP->phonejack box suitable for supporting both SIP and XMPP/GoogleVoice sessions; the latter being my interest.

I'm at a friend's, and scrounged an old "Cobra" phone to use with it. But the phone somehow suffers fom imbalance such that there was an annoying amount of 60 Hz.

I called a friend on the other coast this morning. He is on a PoS*** copper loop of 40Kft plus, and always has hum balance [60 Hz] issues.

But his 60Hz is from another power grid, NOT sync'ed to mine. We could listen to the two grids slowly hetrodyning against each other...

BTW, I gave up on the Taiwan special, and found another phone in the junk box here; this a genuine BSP-NFS 500 set. I bet I'm only Obitalk customer running such. No hum at all with it.

Reply to
David Lesher

Now that is dedication. I've just measured that the voltage coming out of my outlets is rock steady at 125VAC. I suppose I could hook up the scope and measure the frequency but why bother.

Reply to
T

Well - the old joke applies. You put your head between your knees and kiss your butt goodbye.

But the other thing that is rather annoying is the EBS tests. Now not only the broadcast stations conduct EBS drills, but the cable providers do it too.

I've seen a number of times where EAS flashed across the display on the front of my cable box while they were testing.

Reply to
T

What annoys me is how the "alerts" are for things that don't matter, such as a "High wind advisory" in the middle of hurricane Sandy, or for floodwatches in areas forty miles away. You'd think they could get better control over which localities see which warnings.

Bill

Reply to
Bill Horne

The system used by Silicon Valley [Santa Clara County [SCC]] "should" work but I've never received any alerts even when a mass-murderer/ shooter was doing his thing 1/2 mile from my home. The system also doesn't have any "test" mode so one can verify the information that was entered will be used correctly for an alert. Here's the system as implemented in Silicon Valley:

I asked about the system previously in comp.dcom.telecom but my posting never appeared. My original question was "How can they contact 100,000s of people by landline and cellphone in 'just seconds'?".

Here's the system Silicon Valley has more-or-less implemented:

and as far as I can tell it's totally dysfunctional -- a common problem here in California nowadays.

Palo Alto was the last city in Silicon Valley to join the program after abandoning their proprietary Community Alerting and Notification System (CANS) -- that may have been a big misteak (sic) on Palo Alto's part.

Thad

Reply to
Thad Floryan

In the recent storm we've been getting many robot calls from local municipalities. However, municipal boundaries have no correlation to telephone exchange boundaries. so a municipality sends calls out to all landline phones which might be within their town. Some of the alerts are rather cryptic; there is room for improvement.

I don't know how people who only have a cell phone get those messages. We've never signed up for the municipal messages, and it appears they simply dial all lines in sequence.

Our condo has made good use of the robo caller* in this recent storm, including updates on when power would be restored** and other critical utility issues (such as a sewage problem). The condo calls whatever number(s) residents provide them. I get the calls at both home and work which is helpful.

  • Initially they used the robo caller to announce social events, but many found that annoying, and it was also found to be more expensive than distributing a notice the old fashioned way.
** A great many remain without power.
Reply to
HAncock4

The ones in Oklahoma are usually identified by what counties are affected. County lines, of course, are often pretty aribrary, although perhaps not at the time the counties were created.

Wes Leatherock snipped-for-privacy@yahoo.com snipped-for-privacy@aol.com

Reply to
Wes Leatherock

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