Fundamentals of grid stability

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Guest contribution by Rud Istvan

Charles asked if I would criticize this new nonsense. Sure, why not.

The featured article “Science” aims to create an open source grid data resource using 17 European synchronous grid regions to design and test how “this can contribute to the development of new power systems that meet changing needs such as the transition to renewable Energies do justice to energy sources. "NOPE, that doesn't help at all.

The body of this silly paper found smaller fluctuations in the network frequency in larger "isolated" European sub-networks! Of course, larger grids have less frequency fluctuations – something trivial that has been known for many decades. The reasons are intuitive and simple. By definition, larger grids have more generation that feeds the grid, i.e. more grid inertia and at the same time fewer “instantaneous load fluctuations” due to the statistical law of large numbers.

The lattice inertia is just the frequency stabilization that results from the kinetic energy of large rotating generator masses. If the network load increases "immediately", the frequency drops and the generator wants to slow down. Due to the slowing down, however, part of its kinetic rotational energy is also injected “immediately” until the drive source (steam or natural gas in CCGT) can be turned up a little to compensate.

CCGT is particularly good here. It runs 61% at full load, 60% at 80% and 59% at only 40%. The response time of the gas turbine power is literally around a second, no different from a jet engine.

None of these "open source data resources" help with the move to renewable energy. Basic grid electrical engineering (EE) is simple and inevitable when it comes to renewable energies – it is inefficient (investments fall whenever subsidies run out), intermittent (requires underutilized backup generation), and offers no grid inertia (that of large generators automatically with fossil fuels)). EVERYTHING BAD.

The approximately 10 year old CCGT units 4 (375 MW) and 5 (860 MW) from Irsching Bayern illustrate the problems that intermittent renewable energies without grid inertia cause for every grid. The owner wants to take them out of service as they are very unprofitable if they are used primarily as a windbreak rather than a grid load. The federal government refuses to make up the difference, but does not let it close either.

In the larger German picture of renewable energies, Northern Germany exports surplus wind energy to Norway as a promotional gift. This allows Norway to reduce its hydropower. If Germany then needs electricity because the wind is insufficient, Norway winds up its hydropower and sells it to Germany at exorbitant prices. To make matters worse, the German NIMBY crowd is not letting utility companies install the badly needed north-south German transmission links "eyesores" – despite bigger and uglier wind turbines.

A small amount of renewable energy on a large stable grid is not a problem – and this new study is not required. The backup capacity (spinning reserve) and the net inertia are already available. However, as the share of renewable energies in a stable “synchronous” grid increases, these problems increase and become worse. Depending on the network details (e.g. how much flexible hydropower plant), a renewable penetration of more than 8-10% ALWAYS causes additional costs and stability problems. AC network technology has been known for well over 100 years, and nothing “new” can change the established mathematics, physics and electrical engineering (EE).

There are also some "basic EE things" that this new "open source data resource" is ignoring.

First, your “new” network frequency data is almost always available from the utility companies (network operators) as it is necessary for the management of the network. It is recorded both in the power stations and during transmission to substations. Maybe they should have just asked for the utility data instead of collecting their own.

Second, their proprietary super-duper line frequency detectors can be bought almost anywhere to collect their new open source data. Such detectors are a common tool for electricians. A very high quality multi-purpose pocket unit is the Extech PQ3450 power quality analyzer shown.

Third, they are known to have found that grid frequency declines when demand exceeds supply and increases when supply exceeds demand since Tesla first considered generating alternating current using complex numbers (a + bi). The USA is designed for a stable 60 Hertz, EU 50 Hertz. Since electrical clocks depend on the mains frequency, “stable” in the USA is plus / minus 0.2 Hz.

Just for fun (because the above is all well done at WUWT and Climate Etc), we at WUWT also offer an easy math / science challenge for those unfamiliar with AC electrical appliances. (Thanks to a physics book full of hundreds of such challenges, unfortunately more in Chicago than Fort Lauderdale, half of which I reconstructed from memory and half from Google "facts"). It's about right.

Imagine a high voltage AC line between Chicago and New York. (Note: The distance does not play a major role in this challenge, the voltage plays a major role, but it is always “high”.) The challenge: How far does an individual electron charge move during its journey along this transmission line? Choices:

Kilometer meter meter

The speed of light (also known as electromagnetic radiation) is about 299792458 meters / second in a vacuum. However, wires for electromagnetic force (EMF) waveguides are definitely not a vacuum. Their metals have an electrical resistance (technically mains alternating current impedance, a combination of circuit resistance and reactance). Although electrons pushed along by EMF have essentially no mass, they still slow down a lot in metals.

If you skip a little complex math to explain the very simple physics, the reason you buy “fat” DC audio cables with gold connectors is simple: DC current flows pretty evenly across the entire conductor cross-section. A thicker cable will have a uniformly lower cross-sectional resistance (DC speaker output is analog), and gold connections further reduce the connection resistance because gold does not corrode. The result is truer, high-frequency pitch amplitudes. These secondary physics are the reason why “fat” high-voltage direct current transmission lines are preferred for long network distances, such as the above-mentioned underwater connections between Germany and Norway.

The answer to the "fat" power cord is different. Alternating current has a conductive skin effect. In contrast to direct current, alternating current flows mainly in a ring-shaped "skin ring", the thickness of which depends on the frequency (higher thinner), thanks to the interesting alternating current sequences of Maxwell's equations, as in Feynman's "Lectures on Physics" v. explained. . In a “pure” copper conductor, this ring-shaped skin path (the center of the conductor essentially carries no alternating current) is only about 3.2 meters per second. The far more common (cheaper, lighter) aluminum HV transmission conductor is only about 61% copper. In aluminum high voltage transmission lines, electrons move around (3.2 m / s * 0.61) ~ 1.95 m / s at best without considering the oxidation of the skin.

Alternating current is a sine wave that varies x times per second from 0 to plus EMF to 0 to minus EMF to 0 (US 60 Hz, EU 50 Hz). One cycle ranges from zero voltage to max. EMF to zero to opposite polarity. Max. EMF back to zero. The back and forth movement of the EMF is nominally 120 US peaks / second, 60 times in each direction. (Side note: unlike most DC circuits, AC EMF is related to but not the same as voltage.) For simplicity, think of this AC challenge as simply digital rather than a sine wave (all one or all.) from EMF instead of a varying EMF sine wave), thereby eliminating any need for correctly phrasing the calculus challenge. Then the greatest distance that a practically massless electron can travel in its aluminum high-voltage skin is about (1.95 / 60) 3.2 cm, back and forth and back and forth. The actual US (sine wave EMF calculation) response is less than an inch back and forth and the EU less than 2. This is because there is a lot of EMF only near the top and bottom of the sine wave, which is what the Intermediate time slows things down further. Every answer (oversimplified or correct) does not lead to very much electron travel distance (c).

Back to the main topic of this guest post, despite this new European "network research":

Renewable subsidies and investments in them are being reduced everywhere and at all times. They are demonstrably uneconomical, single.

Renewable energies are temporary; However, do not cover the cost of backup for the interruption.

Renewable energies do not offer grid inertia. But don't cover the cost of providing frequency stability with massive synchronous capacitors.

More research and new open source data resources on fundamentally bad statements won't improve it. NEE!

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