Grid Frequency Experiment

[gar]

110628-1241 EDT

I have power back on. It was off for about 2+ hours while they replaced both cross members, fuses, insulators, etc. Originally they were going to also replace the transformer, but did not. That may happen later. Very interesting crew, worked well together.

On Time Error Correction Reliability Standard p 14 under section C may be the reason for Time Error Correction being costly.

So many of the statements are of a qualitative rather than quantitative nature that it is very hard to get a reasoned analysis of why there is a problem other than rules that have been made or may be made. They seem to ignore the effect of devices that are line frequency driven that control something that relates to time of day.

Today after my power was restored I had three LED digital clocks, one oven, and one microwave that had to be reset.

In a derivative report I found some reference that a time drift of 2 or 5 seconds was a criteria to initiate a Time Error Correction.

If Time Error Correction is dropped, then I suspect that a number of unintended consequences will result. Similar problems have occurred with other rules --- Like toilets that don't function correctly because of government rules. Dishwashers and clothes washers that don't get things clean.

It is probably possible to build new devices that may not cost to much to get accurate timing information to low cost devices. For example a central receiver that receives NIST data for a building or portion of a building, then retransmits this data in the building to low cost receivers. Greatest problem may be in large factories, or metal buildings. A lot of industrial timers are in NEMA-4 enclosures.

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[hurk27]

Possibly so. Not so many of those around now, though.

Oh no we are rhyming so

Whats next Rapping:happysad:


There has to be hundreds of thousands of time switch's out there with synchrotron motors in them, one of the most common is a Intermatic T101 or T103 ot Tork controls and there on about every parking lot light system I have seen, not allot of PLC controls yet in this area, some but not many.

I have started using the Intermatic EI600 programmable control with the astronomic clock, you just program and forget it it even tracks the seasons, no photo cell needed, 3 year battery backed up DST ready and easy to program (well if you have a magnifying glass:blink 20 amp rated dry contact out, love these things, feed contactors and control as many lights you want with one.

This one: http://www.smarthome.com/25089/Inte...ronomic-Electronic-In-Wall-Timer-White/p.aspx

 

[Besoeker]

Today after my power was restored I had three LED digital clocks, one oven, and one microwave that had to be reset.

But wasn't that just because of power loss? Like removing the battery from a quartz clock. And unrelated to the absence of a mains frequency for timing purposes?

It is probably possible to build new devices that may not cost to much to get accurate timing information to low cost devices.

Yes. As I posted earlier, the clock in my car is accurate to within a second (it precisely matches the Greenwich time signal*) and automatically updates for seasonal time changes.

*The pips as they are popularly known.

The pips for national radio stations and some local radio stations are timed relative to UTC, from an atomic clock in the basement of Broadcasting House synchronised with the National Physical Laboratory's Time from NPL and GPS.

 

[don_resqcapt19]

You can download a screen saver here that will let you look at the frequency of the Western Interconnect frequency in near real time. I think the actual connection is somewhere in the State of Washington.

 

[gar]

110629-0816 EDT

Besoeker:

The point of my having to reset the clocks is that all of the said clocks are timed based on the line frequency. There is no internal time base, and no standby operation of the clock. This is in contrast to clocks with battery backup and something to provide a temporary clock while in battery backup mode for loss of line power.

In the US, so called "Atomic" clocks do not work well in many locations because of RF signal strength problems. To make these work from the Boulder signal source would require some sort of repeater at the problem destination. Then if we have a real time clock need inside a NEMA 4 enclosure there will need to be an antenna added to the outside of the box.

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[tallgirl]

I have five devices that will be affected -- oven and microwave clocks, water softener and filter timers, and a recirculation timer for the hot water. My inverters hold the power at about 59.95 Hz and those devices all run slow when I drop grid power for any length of time.

That's a LOT of gadgets in an otherwise pretty high-tech house that will be affected.

Based on everything I've read, including the various analyses by different people, this experiment is going to come to a screeching halt shortly into it. A better solution, in my opinion, is to make up the time error during periods of more constant load when running the generators fast or slow is a more predictable process.

If I remember correctly, the maximum expected error is 14 minutes per year, or 2 seconds per day. If the error correction were scheduled over a 4 hour period, that's 1 part in 7200, or less than 0.01Hz. Hopefully they'll go that route, rather than allowing error to accumulate.

 

[Besoeker]

110629-0816 EDT

Besoeker:

The point of my having to reset the clocks is that all of the said clocks are timed based on the line frequency.

Are you sure that they use line frequency?
We have a digital clock on our coffee pot that has to be reset if it is unplugged. It gains ever so slightly over a period so I would have to conclude that it is not line frequency dependent. Maybe it's the same for the cooker and our microwave oven.

For anything made for a world market, and much is these days, it can't use line frequency to operate clocks.

 

[iwire]

Most all of the mechanical time clocks we install use a synchronous motor.

When given the choice I still use the old style mechanical time clocks over the electronic versions. The electronic units die early and often while the old mechanical ones do not fail ...... or at least I can never remember replacing a broken one.

http://www.nsiindustries.com/products/tork/mechanical-time-switches.aspx

 

[rcwilson]

You can download a screen saver here that will let you look at the frequency of the Western Interconnect frequency in near real time. I think the actual connection is somewhere in the State of Washington.

That neat screen has been out of service for about a year (or it is blocked by my corporate firewall). I think it was for some "Smart Grid" research to link load control with generation and frequency.

But you can still see a trace of a large fault event that tripped a lot of load and generation on the west coast, by clicking on the simulation tab at the top. You can see bumps where load was dumped (frequency goes up) and where the governor action finally stabilized the system.

 

[don_resqcapt19]

That neat screen has been out of service for about a year (or it is blocked by my corporate firewall). I think it was for some "Smart Grid" research to link load control with generation and frequency.

But you can still see a trace of a large fault event that tripped a lot of load and generation on the west coast, by clicking on the simulation tab at the top. You can see bumps where load was dumped (frequency goes up) and where the governor action finally stabilized the system.

Bob,
It must be blocked as it is my screen saver on my home computer and it works fine. I can't get it here at work as it is blocked by the corporate firewall.

The Grid Wise plan was to put frequency monitoring devices in appliances and to have them shut down as a "demand response" on frequency drop. I am not sure if they are still working on that or not.

 

[tallgirl]

Bob,
It must be blocked as it is my screen saver on my home computer and it works fine. I can't get it here at work as it is blocked by the corporate firewall.

The Grid Wise plan was to put frequency monitoring devices in appliances and to have them shut down as a "demand response" on frequency drop. I am not sure if they are still working on that or not.

As far as I know, the GridWise project was completed and was considered to be successful. It's been years since I read the information that came out of it, but my recollection is that they had a small number of devices that could be retrofitted to turn off based on a frequency signal.

I was part of a patent team -- about 7 or 8 of us total -- who looked at what was done with GridWise and found several flaws, then wrote about 3 dozen patent applications to improve on all those flaws (heh).

One of the problems with GridWise is that there was no focus on "Just how cooperative =are= you?" as a metric. So we came up with a way to measure how well a customer interacts with the grid and grid frequency.

As an aside I have the sinking feeling that the "experiment" is already being conducted inside ERCOT -- I'm seeing the frequency ranging between 59.7 and 60.3 and it used to be much tighter than that. Could be the miserable hot weather, but it was miserable hot before the experiment was announced.

I made a mistake with my earlier calculations -- I based it on 14 =minutes= per year, not the maximum 14 seconds per day in the presentation. Fourteen seconds per day over a four hour period is 0.06Hz.

 

[don_resqcapt19]

...
As an aside I have the sinking feeling that the "experiment" is already being conducted inside ERCOT -- I'm seeing the frequency ranging between 59.7 and 60.3 and it used to be much tighter than that. Could be the miserable hot weather, but it was miserable hot before the experiment was announced.
...

Well that is the least stable of the 3 grids in the US. The Eastern interconnect is the most stable.

 

[gar]

110629-2205 EDT

Besoeker:

The three digital LED clocks I referenced are line frequency timed. They quantize to one minute and over a year's time, if there is no long drop in voltage, there is not a 1 minute error. Same for the oven and microwave, no error. A long drop and they go into a flash mode with some random time.

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[tallgirl]

Well that is the least stable of the 3 grids in the US. The Eastern interconnect is the most stable.

Right, but it seems to be less stable over the past few weeks than before.

What I ought to do is reset the clock on the stove as close as I can to the atomic clock on the wall behind it and see if it's moving relative to the WWV time. Of course, I will then forget all about this thread ...

 

[gar]

110630-1045 EDT

What is a definition for "instantaneous frequency" and how is it measured?

When I made some limited line frequency measurements I used zero crossing detection, and measured the time from a start positive zero crossing to the 100th one following the start. This is an averaging time of about 100/60 = 1.66666 .... seconds. The zero crossing error is probably less than 0.01/40 = 0.025% relative to peak AC voltage.

I did not have a means to automatically record values and thus took only 36 consecutive samples. There was manual recording time between measurements so the measurements were not adjacent samples. Recording time was about double the sample time.

The minimum frequency was about 59.994, and the maximum about 60.013. The maximum positive deviation was about double the maximum negative deviation. The negative deviation were relatively uniformly distributed. Where the positive deviations were clustered into about 6 groups. The overall sample size is too small to get much information.

My timing measurement accuracy was on the order of 1 part in 10,000,000, 0.1 microsecond. System noise probably reduced this to 1 microsecond.

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[T.M.Haja Sahib]

110626-1953 EDT

hurk27:

I would agree that many new devices may use an internal clock, and many of those may not hold time accuracy over a long time as well as a line synced clock.

Unless you have a really high quality quartz crystal oscillator your drift per year is likely to be many seconds. Note: 1 second within a year requires stability and accuracy of 1 part in 31,557,600 using a 365.25 day year. For 1 minute accuracy you need 1 part in 525,960. You can not afford to put a good quality wristwatch crystal in an inexpensive clock. Even if clocks that run from 60 Hz power have a microprocessor internally that does not mean a highly stable or accurate oscillator is used. Thus, syncing to line frequency may be the best source of timing information for long term correctness. Line disturbances are not a reason for not using the line for timing information.

My BK 1822 frequency meter has the following specification on the time base:
Frequency 10 MHz.
Setability +/-0.1 ppm (+/-1 Hz)
Line voltage Stability Less than +/-1 ppm with a +/-10% line voltage change
Temperature stability Less than +/-0.001% (+/-10 ppm) from 0 thru 50 deg C
Maximum aging rate +/-10 ppm/year
An oven option provides +/-1 ppm for the above temperature range.

This is a far better crystal than in many low cost items.

But getting time sync infromation from NIST is probably the ideal method for many devices.

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Hi,Any on line source (or information at hand) on how power quality issues affect the performance of digital clock connected to the grid? Thanks.

 

[T.M.Haja Sahib]

Interesting thought but wouldn't that mean that they would have to provide that extra capacity. I think they would be self motivated to run under frequency to reduce load.

Operating static equipments like transformers with under frequency presents serious fire hazard due to overheating.

 

[wirenut1980]

Hi,Any on line source (or information at hand) on how power quality issues affect the performance of digital clock connected to the grid? Thanks.

If there is distortion in the voltage waveform, you could get extra zero crossings, which could cause clocks to run fast. But that is only if the clock is relying on the voltage to keep time. Welcome to the forum!