Path: csiph.com!aioe.org!.POSTED!not-for-mail From: Martin Brown <|||newspam|||@nezumi.demon.co.uk> Newsgroups: sci.electronics.design Subject: Re: OT: Current standard for watch precision Date: Wed, 8 Feb 2017 09:01:21 +0000 Organization: Aioe.org NNTP Server Lines: 40 Message-ID: References: <27ll9c1rn1mg14c2t9rgtpvee6sedka25n@4ax.com> NNTP-Posting-Host: 3GhpzT84sg/pRzW4FgEbGg.user.gioia.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@aioe.org User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 X-Notice: Filtered by postfilter v. 0.8.2 Xref: csiph.com sci.electronics.design:446759 On 08/02/2017 08:37, rickman wrote: > On 2/8/2017 3:25 AM, upsidedown@downunder.com wrote: >> On Tue, 7 Feb 2017 14:52:09 -0800 (PST), Lasse Langwadt Christensen >> wrote: >> >>> on the page Jeff linked to it says they can catch up ~17 seconds a day, >>> once they get 20 seconds out of sync >>> >>> and it is just country wide, the synchronous grid of Continental Europe >>> 667 gigawatts in 20 some countries >> >> There are thousands of generators connected in parallel and the >> fluctuating frequency ensures that there are proper load sharing >> between generators. This method has been used for more than a century. > > So how is the average frequency maintained? What actually controls the > long term frequency of the grid? If it were just the load sharing > driving the frequency up and down as the loads and generators vary, the > frequency would wander with no fixed average. The long term average is very carefully maintained by running the grid faster usually at night to catch up when the load is lowest - a quirk that used to annoy astronomers back in the days when synchronous 60Hz motors were used on some telescope drives. If you watch the realtime grid frequency display at times of peak load on for example UK gridwatch you will see the relation between load and frequency. They try never to get more than 0.2Hz out for an extended period and will bring in fast generators like the pumped hydro storage and gas turbines if it does or typically if peak load is anticipated. http://www.gridwatch.templar.co.uk/ Big football match half time is particularly hard on the grid at this time of year as everyone goes to put the kettle on at once and load is already pretty close to the upper limit. Not much margin on UK capacity. -- Regards, Martin Brown