[time-nuts] Line Frequency standard change - Possible ?

Magnus Danielson magnus at rubidium.dyndns.org
Sat Feb 11 11:51:39 EST 2017


I know. In practice many of the operators in the US is working together 
to get smarter, share experiences and learn from each other and others.
Good folks.


On 02/11/2017 04:08 PM, Bob Camp wrote:
> Hi
> To be fair to these guys, they have a number of challenges that have nothing to
> do with technology. They cross link to other companies and have little control
> over how each one operates. Here in the US, we have multiple regulatory
> agencies (it happens at the state, federal, and international level).  they all are involved
> in any change. That makes for a very long and drawn out dance when you fiddle
> with this or that. Also, in many cases are the shareholders in the company
> who seem to have goals as well ….
> Not an easy thing.
> Bob
>> On Feb 11, 2017, at 5:22 AM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
>> Work is already underway to improve the relicense of power grid operations. They is smarting up quickly. The PMU/synchrophasor measurements depend on UTC and before it can be used full-blown for operation the single point of failure needs to be handled.
>> Cheers,
>> Magnus
>> On 02/09/2017 11:19 PM, Peter Reilley wrote:
>>> Isn't this "hard" lock to UTC creating a single point of failure? A
>>> solar burst, an EMP, or
>>> a software error could leave us all in the dark.   After all, smart
>>> inverters could be
>>> programmed to act like big lumps of rotating iron and be compatible with
>>> the current
>>> system.
>>> Pete.
>>> On 2/9/2017 4:31 PM, Poul-Henning Kamp wrote:
>>>> --------
>>>> In message
>>>> <4FBDD81DDF04FC46870DB1B9A747269202916B42 at mbx032-e1-va-8.exch032.ser
>>>> verpod.net>, "Thomas D. Erb" writes:
>>>>> I was wondering if anyone was familiar with this proposal, is this
>>>>> a uncoupling of line frequency from a time standard ?
>>>> The interesting thing about this is that all research and experiments
>>>> (for instance on the danish island Bornholm) indicates that the only
>>>> way we stand any chance of keeping future AC grids under control in the
>>>> medium term is to lock the frequency *hard* to UTC.
>>>> Its a very interesting topic.
>>>> In the traditional AC grid power is produced by big heavy lumps of
>>>> rotating iron.  This couples the grid frequency tightly to the
>>>> power-balance of the grid:  If the load increases, the generators
>>>> magnetic field drags harder slowing the rotor, lowering the frequency
>>>> and vice versa.
>>>> This makes the grid frequency a "proxy signal" for the power balance,
>>>> and very usefully so, because it travels well and noiselessly through
>>>> the entire AC grid.
>>>> The only other possible "balance signal" is the voltage, and it
>>>> suffers from a host of noise mechanisms, from bad contacts and
>>>> lightning strikes to temperature, but worst of all, it takes double
>>>> hit when you start big induction motors, thus oversignalling the
>>>> power deficit.
>>>> Where the frequency as "proxy" for grid balance reacts and can
>>>> be used to steering on a 100msec timescale, you need to average
>>>> a voltage "proxy" signal for upwards of 20 seconds to get the
>>>> noise down to level where you don't introduce instability.
>>>> The big picture problem is that we are rapidly retiring the rotating
>>>> iron, replacing it with switch-mode converters which do not "couple"
>>>> the frequency to power balance.
>>>> For instance HVDC/AC converters, solar panel farms, and increasingly
>>>> wind generators, do not try to drag down the frequency when they
>>>> cannot produce more or drag the frequency up when they can produce
>>>> more power, they just faithfully track whatever frequency all the
>>>> rotating lumps of iron have agreed on.
>>>> As more and more rotating iron gets retired, the grid frequency
>>>> eventually becomes useless as a "proxy-signal" for grid balance.
>>>> Informal and usually undocumented experiments have already shown
>>>> that areas of grids which previously were able to run in "island"
>>>> mode, are no longer able to do so, due to shortage of rotating iron.
>>>> One way we have found to make the voltage a usable fast-reacting
>>>> proxy for grid power-balance, is to lock the frequency to GNSS at
>>>> 1e-5 s level at all major producers, which is trivial for all the
>>>> switch-mode kit, and incredibly hard and energy-inefficient for the
>>>> rotating iron producers.
>>>> The other way is to cut the big grids into smaller grids with HVDC
>>>> connections to decouple the frequencies, which allows us to relax
>>>> the frequency tolerance for each of these subgrids substantially.
>>>> This solution gets even better if you load the HVDC up with capacitance
>>>> to act as a short time buffers, but the consequences in terms of
>>>> short circuit energy are ... spectacular?
>>>> (It is already bad enough with cable capacitance in long HVDC
>>>> connections, do the math on 15nF/Km and 100.000 kV yourself.)
>>>> All these issues are compounded by the fact that the "50/60Hz or
>>>> bust" mentality has been tatooed on the nose of five generations
>>>> of HV engineers, to such an extent that many of them are totally
>>>> incapable of even imagining anything else, and they all just "know"
>>>> that DC is "impossible".
>>>> In the long term, HVDC is going to take over, because it beats HVAC
>>>> big time on long connections, and it is only a matter of getting
>>>> semiconductors into shape before that happens.  That however,
>>>> is by no means a trivial task:  It's all about silicon purity.
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