Power & Frequency

[(unknown)]

Hello everyone,

Can anyone please tell me, what happens to the frequecy when the line power is incresed or decreased?

[finnsawyer]

Define "line power".  Are you talking about grid power or windmill power?  In general when you try to grab more power the generator providing it will slow down slightly reducing the frequency.  Controlling circuity will then have to convince the energy source to provide more power (from steam, water, reciprocating engine, etc).  This takes place so quickly that In the case of the grid you wouldn't notice any change in frequency unless your name happens to be Tesla and you are experimenting with broadcast power, in which case you might blow the generator.  In the case of a windmill you can't get any more power than what the wind has, so the windmill will slow down, frequency will drop, and in severe cases the mill may stall.  A lot depends on whether the mill was operating at designed TSR or was over speeding when the extra demand occurred.  For a drop in power demand the windmill speeds up and its frequency increases.  

[dinges]

Utility line power can be increased and decreased without effect on frequency (50Hz over here, 60 Hz in USA).

If load increases, this may slightly pull frequency down; the guys at the powerplant increase power so voltage and frequency are back within limits.

I don't see any problem here, why do you ask this question?

Peter,

The Netherlands.

[Nando]

You may have, in your head, clear concepts for your questions, but unhapply no one in this group has the capability of reading your mind and really get the true well defined questions for you to get a reasonable logical answers to your questions.

So, please, assume that we do not know anything about you and your plans and you need to detail, quite carefully, what your concepts and questions are for us to understand what is going on.

Nando

[wooferhound]

I have heard that the common clocks don't really keep time, They count the line frequency. Even the clocks with motors are syncronized to the line frequency.

•      60 cycles = 1 second
  
•  216000 cycles = 1 hour
  
• 5184000 cycles = 1 day
  
  

The power company keeps track of the frequency that they put out and adjusts it to be very accurate by the end of the day. If you try to power a clock from an inverter, then your timeclocks will drift according to the frequency that your inverter puts out, unless you have a grid tied inverter.

[finnsawyer]

In the case of battery operated clocks a crystal oscillator is used.  In this spirit, if you are willing to invest a decent sum of money, I believe I can build an oscillator that will keep time to one part in 100 million.  That is, it will go off by one second in about 1200 days.  Cheers.

[Nando]

W O O F :

What you have "heard" is just reality, any time piece counts pulses, even the atomic clocks that are now the time reference to an error of one second in billions of years.

You take certain family of stable pulses and count them and display them ( region of them ) to cover the human area of interest ( from a fraction of a second to years -- as desired) -- the count is done in a way ( mostly done in a decimal format with defined selection ( like 60 seconds or 28 days in a certain month of the year - - including changes in leap years - or periodic second adding or removal following the earth and moon time variations in space).

The GRID frequency is averaged to maintain the 60 HZ in USA and it is controlled with a atomic standard that the power plants have as a reference-- AVERAGED because the generator varies with variable loading or guide settings or water availability and since the plants are located all around the country and in Canada each one generates its frequency for the local area that is maintained to a common reference with a frequency angle delay to take in account the time for the energy to travel down the transmission lines so when two power plants energies meet, the angle between both is zero to avoid a MAJOR SHORT CIRCUIT between them.

It is a complicated system that sometimes may "crash" -- there are many mini or micro crashes that are constantly corrected in a fly -- we humans do not notice them because the equipment has some capabilities to reduce the effects -- too long to explain here.

The AVERAGED TIME is done continuously during the day, and not at the end of the day -- end of the day -- around 50 or more years ago -- not now with the electronics that we now have.

As curious thing. I have developed small hydro electric plant Frequency controllers that do such a thing and maintain a clock attached to its frequency with an error of about 2 to 5 seconds a month.

Recently, I was asked to get one small hydro electric plant referenced to a GPS reference for an accuracy of about 2 seconds a year -- when the interested party received the design quote they almost had a heart attack -- about half of the cost of the hydro system they have installed in their farm -- for the owner to be able to connect its AC table alarm clock ( U$ 10 ).

Nando

[(unknown)]

Thank you all for replying.

I will make myself clear.

I am a member of Energy research group, in my university, headed by my supervisor.We are working on a project where we can use the excess power generated from a wind turbine to run the Electric Thermal Storage (ETS).

Now,ETS is a space heating device capable of storing the heat until it is needed.

What we are planning to do is,

whenever there is excess power from a wind turbine, we can use it to run ETS which will convert that power in heat and store that heat for a period when there is not enough wind.

This is a Utility scale project, so the utility will have to inform its consumers whenever there is an excess power, by sending some kind of signal, so that the ETS can be turned on.

We were planning to use the existing power lines for sending this signal, but what if the signal is lost? So if the excess power affects the frequency, we can place a frequency sensor at every consumer's house and then they can know when to turn on the ETS.

I can go on and on, but I think this is more clear now.

Thanks!!

[dinges]

Isn't the solution much easier than using transmitters and receivers?

Simply monitor voltage and frequency of your generator. When load drops, voltage should go up, and frequency too. You could set a specific limit of voltage, over which your ETS would kick in?

Seems like a much simpler idea to me, without any communication lines necessary (in fact, you are using the power line itsself to monitor power capacity vs. power usage).

Unless I'm overlooking something, of course.

Besides, 'excess power from a windgenerator'? If it's a utility scale project, and there extra windenergy available, instead of storing that energy as heat, wouldn't it be easier to phone/transmit data to your local power plant to turn down the 'heat' a little, so the windgennies would see more load? That way you harvest maximum of windenergy, at the same time reducing consumption of non-RE energy types?

Just some thoughts that spring to my mind. I don't know within what limitations your project must operate, of course.

Peter,

The Netherlands.

[dinges]

I had intention to build a project for VERY accurate time/frequency; basically it locked to a video-carrier, as broadcast by our local TV stations (the 15.625kHz line frequency is locked to a Cesium or Rubidium time standard over here). Very simple project, only one problem: TV stations are scheduled to go out of the ether in 2007 (seems it will take a few years longer though), while cable TV, esp. digital TV, is way too inaccurate.

Alas. It was a very nice project, simple to build (basic digital stuff), and very accurate (after the PLL stabilized/locked, which takes a few hours). Basically, you would get atomic clock accuracy; I remember that at 10GHz, I would have an error of only a few Hz...) But I won't bother building such a project if I can only use it for 2-3 years in the future (the way I construct/work on projects, it would a year just to finish this (simple) project )

There once was a time that our line connected clocks were known to be inaccurate, but since the power companies started adding pulses (I think it was at the end of the day too) to get to (50Hz*60 seconds*60minutes*24hours=???pulses), these clocks are very nice timekeepers.

Peter,

The Netherlands.

[Gary D]

 Neekee, in my state (Pennsylvania) in the U.S. there is a system of load control in place. The electrie co-op sends out a signal during power peaks and shuts off thousands of electric waterheaters via a control switch (shamefull more households don't have them installed).

 You are trying to produce a load (ets storage) during low demand and excess winds(using wind power wisely). Hopefully you or your advisor could contact a U.S. electric co-op group that could give you advice on such a worthy project.

 Unfortunatelly the energy producers in the U.S. would demand two meters, or what's called a time of day meter and charge higher rates even when there was excess electric avalible during the day. Consumers rule here, and if there is no economic incentive (or even a penalty), few would participate. Perhaps in the future, our State and Federal governments will actually decide to take conservation and load control seriously (on both low demand and peak demand. Good luck on your endevor! Gary D.

[richard]

  biuld  a 60 K.C.  rec. Lock on to WWVH in colo.  + or - 0.0000001 cps. in 100 years.

[Gordy]

Neekee,

To add to what Gary said.

 Here in MN (US) my power coop has had a "Off Peak" and "Dual Fuel" program going for 20+ years, for water heating, air to air heat pumps/ air conditioning, resistive heating, ETS heating, ect. These do require a second radio controled meter that is charged at the "Off peak" rate of 3.5 cents per kw, rather than the standard 8.5 cents per kw rate. I've benn on the program sence 1990 and love it and the $$$ savings.

Gordy

[Nando]

Peter:

The power companies do not add pulses, they force the 50 HZ in Europe to drift up or down to maintain the 50 HZ averaged in 24 Hours or so, this 24 hours may be different in Europe.

Right now there is a better system and it is the GPS signals referenced to high precision time reference, most all good GPS receivers have an timed output locked to the GPS frequency that may give an error of one second in about 3000 years.

Nando