This is sorta part 1 of 2 that I have been meaning to blog about for a while….
My adventures in mains frequency measurement came from an Opto customer that wanted to make a device that started a generator if the mains frequency dropped a set amount (less than 1Hz).
Some of my co-workers wanted to know why it would drop… I have no idea how I knew the answer, I just did. Not that it mattered at the time, but I called it the wrong thing, I called it ‘the kettle effect’, it’s not, it’s called ‘TV Pickup’.
https://en.wikipedia.org/wiki/TV_pickup
Television pickup is a term used in the United Kingdom to refer to a phenomenon that affects electricity generation and transmission networks. It often occurs when a large number of people watch the same TV programmes while taking advantage of commercial breaks to operate electrical appliances (particularly kettles), thus causing large synchronised surges in national electricity consumption.
Why the UK? Because of the small physical size of the country (and thus power grid) and because of the high density of population.
The same mains frequency shift can happen in Texas because they are not connected to the rest of the USA power grid (another blog for another day).
The Opto customer is working with the UK guys first because they have more of a problem than Texas…. Why is this a problem?
Because the power grid can not store energy. Simple as that. Every watt produced and pumped into the grid must be consumed by someone somewhere at the exact same time.
It is really something to stop and consider this TV Pickup effect…. A tv show gets to a commercial break and millions of people put the kettle on for a cup of tea, and boom the grid is hit with the sudden need for a bunch of power that the grid itself can not provide.
How much of an issue is it?
The largest ever pickup was on 4 July 1990 when a 2800 MW demand was imposed by the ending of the penalty shootout in the England v West Germany FIFA World Cup semi-final.
2.8 gigawatts. In a few seconds, please… Is that too much to ask? I would like my cup of tea…. Oh, and if the power is not there, the lights, tv and kettle are going to turn off in a blackout event, and that is going to take even more power to basicly reboot the nation.
Stop and think about that. 2800Mw of power spun up and injected in the grid in a few seconds…. yeah, right… no worries mate…. I got this….
To prepare for pickups the team runs a computer program that compares the current day with corresponding periods over the past five years to predict the size of demand, and studies TV schedules to anticipate demand from popular shows like Strictly Come Dancing.
Yep, that’s right, the power station tracks the popularity of tv shows. Amazing. Cool and a little scary. What have we become?
How can you make that much power that quick?
The shortest lead-in times are on pumped storage reservoirs, such as the Dinorwig power station that has the fastest response time of any pumped storage station in the world at just 12 seconds to produce 1320 MW. Once the longer term fossil fuel stations, which have response times around half an hour, and nuclear power stations, which can take even longer, come online then pumped storage stations can be turned off and the water returned to the reservoir.
In the case of the UK, pumped water. They pump water up to a reservoir overnight and then when they need it, they just open a valve and the water flows down and spins up the generator pretty quick.
Of course the same thing can happen the other way as well….
The Grid also plans for the opposite effect, a co-ordinated mass switch-off of appliances. Boxing Day is consistently, according to one employee, “the lowest of the low” power usage. At midday on 5 January 2005 a three minutes silence in remembrance of the Boxing Day Tsunami resulted in a 1300 MW temporary drop in consumption followed by a sudden 1400 MW rise. Similar, though smaller, switch-offs occur annually at 11 am on Remembrance Day. These switch-offs occur during the day time, so they are smaller than pickups seen at night when more electrical appliances are likely to be in use. National Grid argued against the mass switch-off originally planned for the Live Earth and Planet Aid events as these would have resulted in highly unpredictable demands for electricity and would have generated more carbon dioxide than would have been saved. These events were subsequently cancelled.
I don’t know about you, but I found all this just amazingly fascinating.
The automation, the engineering and people involved in keeping the grid and thus us all happy and healthy is just astonishing. People go probably go their whole lives without giving it a second thought….. I mean, it’s just me, making a cup of tea during a TV commercial…..
Because I can and because I am so fascinated with this topic I am still monitoring the mains frequency at my house and it’s been rock solid.
I added some code start of September to grab the max and min readings every second and latch it.
In this screenshot from today you can see the max and min and when they occurred. Only 0.117 Hz variation in all this time. Amazing.
That said, SoCal is part of a very big grid.
Opto’s customer that is starting the generator in the UK would see way more variation than this in a single day, and that no doubt is their business model. Get that generator started and lift the grid a little. Lots of people starting generators in anything under 12 seconds could really make a big difference.
Ok, part two is all about the duck curve (no sneaky googling what it is), and yes, this time, I have the name right……
