Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: Bill Sloman Newsgroups: sci.electronics.design Subject: Re: The Spanish Grid Drop-out - recently released information. Date: Thu, 15 May 2025 16:18:16 +1000 Organization: A noiseless patient Spider Lines: 89 Message-ID: <10040vj$302p5$1@dont-email.me> References: <0l6fflx9t.ln2@Telcontar.valinor> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Thu, 15 May 2025 08:18:28 +0200 (CEST) Injection-Info: dont-email.me; posting-host="b1364c7858883f66cd27867401c59443"; logging-data="3148581"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+9KrrsGpVpV2Wl77AF1XkbidnW8aOCqd0=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:GJVO1MfWaO5ZWpgy1ZPsu+7tumk= X-Antivirus-Status: Clean X-Antivirus: Norton (VPS 250515-0, 15/5/2025), Outbound message In-Reply-To: <0l6fflx9t.ln2@Telcontar.valinor> Content-Language: en-US On 15/05/2025 5:14 am, Carlos E.R. wrote: > On 2025-05-14 16:16, Glen Walpert wrote: >> On Tue, 13 May 2025 07:50:36 -0700, Don Y wrote: >> >>> On 5/13/2025 6:26 AM, Glen Walpert wrote: >>>>> I don't think that using broadcast radio for real time mains grid >>>>> control is a good idea. It would be far too unreliable. >>>> >>>> Point to point RF links have been in use in (mostly hard wired) grid >>>> control SCADA (System Control And Data Acquisition) systems for at >>>> least 30 years, which is when a former employer did some work on a >>>> SCADA upgrade project for the Egyptian Electrical Authority.  A search >>>> on 'SCADA radio link' will turn up several vendors. >>> >>> And they used these to control instantaneous frequency and phase?  Or, >>> just coarse data collection and /supervisory/ control? >> >> SCADA is used to monitor and control the grid, where control is done in >> real time by adjusting the set points for real and reactive power at all >> controlled power sources.  A small percentage of sources being >> inaccessible degrades control by an insignificant amount. >> >> Real power is regulated by the prime mover governors, which must be >> operated in droop mode in order to share the load (the speed set point is >> reduced with increasing load).  The grid Hz/Gw figure which has been >> mentioned is not directly related to generator inertia, where >> insignificant energy is stored, it is the aggregate droop setting of the >> prime mover governors feeding the grid.  After speed/frequency shift (the >> governors only measure shaft speed) due to a load change the grid control >> center adjusts the governor set points to bring the frequency back to >> normal. >> >> Voltage regulation is entirely separate and is done by setting the >> reactive power output of sources, again by adjusting set points in real >> time over SCADA (or one of the other approved standard comm protocols). >> This is a bit complex for a quick explanation but is described in detail >> in any decent text covering synchronous generator control. >> >> Voltage regulation is more likely to be a stability issue than frequency. >> If you take two widely separated generators or sets of locally paralleled >> generators at two power plants which are optimally tuned for stand alone >> operation and connect them with a long transmission line, voltage will >> begin to oscillate due to the time delay in locally detecting changes in >> the other plants output.  Detuning the regulators to achieve stability >> results in inadequate response to load changes - thus central control of >> both plants over SCADA. >> >> Large generator voltage response time is limited by the L/R time >> constant, >> which will be in the 10's of seconds, over a minute for some large multi- >> pole hydroelectric generators.  Inverters can respond much faster, with >> potentially worse stability issues, and dividing power sources into many >> small units does not make stability any easier, you still can't set >> optimal tuning parameters for widely separated groups of sources which >> will be both stable and fast, central control of some percentage of >> source >> set points is required.  This problem and it's solution is well >> understood >> and the current generation of inverters are designed to allow remote >> control of set points. >> >> In the US more than 2/3 of all solar power is utility owned 10 MW or >> larger and all of this is under central grid operator control, so no >> stability issues there. >> >> More intermittent power sources need more batteries, which are being >> deployed by utilities as fast as they can be manufactured, being far >> cheaper then peaking gas turbines, the most expensive of power sources. >> >> > 55287560/us-energy-storage-industry-commits-100-billion-investment-in- >> american-made-grid-batteries> > > Wouldn't it be easier to have the entire distribution network using DC? > > just saying with a glass of wine in my hand :-) That's probably correct, but it wouldn't be cheaper. It's probably true that taking DC down to the sub-station level could be cheaper, with today's technology, if you were starting from scratch, but since that kit is already there you would be throwing away a lot of big expensive transformers from the next level up, and replacing them with a lot of big, expensive - if less expensive - inverters. It would take a lot of capital investment to make the switch, and the people who operate the grid are adminstrators rather than entrepreneurs. -- Bill Sloman, Sydney