There are 3 electricity essentials – that the power source and its delivery to homes and businesses be: 1) reliable; 2) secure; and 3) affordable. Which means that wind power – a wholly weather dependent power source, that can’t be stored and costs 3-4 times the cost of conventional power – scores NIL on all three counts.
With the wind power calamity unfolding in South Australia, even mainstream media hacks are starting to take an interest in electricity generation which – before South Australia’s recent experience of statewide blackouts, routine load shedding and skyrocketing power prices – was something that the last few generations of Australians have taken for granted.
In an effort to educate, STT has attempted, once or twice, to lay out the electricity generation basics in clear and simple terms – that even journalists might understand.
In this post we’ll start with a primer from the AEMO about what’s required to maintain the integrity of a functioning electricity grid. [Note that the term Power Electronic Converter (PEC) is the euphemism used for wind and solar power generation.]
Fact Sheet: System Strength
What is System Strength?
System strength is an inherent characteristic of any power system.
System strength is important as it can materially impact the way a power system operates.
System strength is usually measured by the available fault current at a given location or by the short circuit ratio (the ratio of the short circuit current at a point in the grid with the current at that point under open circuit conditions and with normal voltages).
Higher fault current levels are typically found in a stronger power system, while lower fault current levels are representative of a weaker power system.
A high fault level, or high currents following a fault, could be viewed as the generation on the grid responding strongly to the drop in voltage at the fault – trying to restore the situation. Similarly a high short circuit ratio at a point in the grid is a measure of the strength of the response to any faults in that area.
Fault currents vary around the grid both by location and by voltage level. The fault currents are higher in areas close to synchronous generation and lower in areas further away from this generation. System strength reduces with increasing amounts of power electronic converter (PEC) connected generation, along with the displacement of synchronous generation which contributes more to the fault current.
What are the Characteristics of Strong and Weak Systems?
Power systems with a high quantity of on-line synchronous generation and very little PEC connected generation provide larger fault current and are categorised as strong systems. This is manifested by the ability of the power system to maintain stability in response to various types of disturbances.
Parts of the power system with PEC connected generation which are distant from synchronous generation are more likely to be weaker. Low system strength generally leads to increased volatility of network voltages during system normal and disturbance conditions. Low system strength can also compromise the correct operation of protection systems, and result in PEC connected generation systems disconnecting during disturbances.
Some weak systems are easy to identify, for example, an isolated part in the system with no nearby synchronous generation. In other parts of the power system where there is multiple concentrated PEC connected generation, weak systems can only be identified through complex power system studies conducted by engineers using detailed models.
Voltage Management in Strong and Weak Systems
Strong power systems exhibit better voltage control in response to small and large system disturbances. Weak systems are more susceptible to voltage instability or collapse.
Increasing Connection of PEC Generation (Wind Turbines)
Generation that is interfaced to the network using PECs requires a minimum system strength to remain stable and maintain continuous uninterrupted operation. Different types of converters use different strategies to match their output to the frequency of the system while maintaining voltage levels and power flows. In a weak system, these can fail to operate correctly through even relatively minor disturbances.
Operation of Protection Equipment in Weak Systems
While weak systems are not new to system operators, they are attracting greater attention following the rise of large scale PEC connected generation in the power system (more wind turbines. Protection equipment within power systems work to clear faults, prevent damage to network assets and mitigate risk to public safety.
Protection equipment may be triggered when the current following a fault exceeds the protection activation point, or by the impedance calculated from this current. Weak systems exhibit lower fault current relative to the strong networks. In a weak system, protective equipment which is programmed to activate on measured current or the ratio of measured voltage to current, could be susceptible to unintended operation or failure to operate.
So much for the principle and theory, now let’s take a look at an inherently ‘weak system’ – thanks to the experiment being conducted in South Australia:
The price of living with ‘PEC’ – ie trying to run on sunshine and breezes – is paid for with wrecked electrical appliances and – when the system shuts down to protect itself from wind power surges and collapses – the failure of whole local systems.
The latter has been part and parcel of life for commuters on Adelaide’s Seaford/Tonsley electric train line for months now: South Australia – Wind Powered Train Wreck: Power Supply Chaos Strands Thousands of Commuters
While the wind industry, its parasites and spruikers keep talking about ‘integration’ of their beloved power source, the actual result is ‘disintegration’: of local systems within the grid (eg the Seaford/Tonsley line); and collapses of the entire grid: Wind Industry’s Armageddon: Wind Farm Output Collapse Leaves 110,000 South Australian Homes & Businesses Powerless
In the video that follows, an electrical engineer, Andrew Dodson explains in detail the lunacy of trying to distribute wind power via a grid deliberately designed around on-demand generation sources.
STT recommends it to anyone with even the vaguest interest in how our electrical grid works (and that must now surely include anyone unlucky enough to hang their hat in South Australia, including the Seaford/Tonsley line’s ‘occasional’ commuters).
At the simplest level, think of our distribution grid as akin to a mains water distribution system. In order to function, the pipes in such a system need to be filled at all times with a volume of water equal to their capacity and, in order to flow in the direction of a user, the water within the pipes needs to be maintained at a constant pressure.
Where a household turns on a tap, water flows out of the tap (in electrical terms “the load”); at the other end an equal volume of water is simultaneously fed into the system and pumps fire up to maintain the pressure within it (although gravity often does the work).
In a similar fashion, an electricity grid can only function with the required volume of electricity within it; maintained at a constant pressure (voltage) and frequency (hertz) – all of which fluctuate, depending on the load and the input.
What Andrew Dodson makes crystal clear is that these essential certainties (essential, that is, to maintaining a stable and functioning electricity grid) have been tipped on their head, as a result of the chaos delivered by wind power.
What Andrew has to say about wind power, in general, has special pertinence to Australians, not just South Australians.
The Federal Coalition government helped lock in a $45 billion electricity tax – which is to be directed at wind power outfits; and for no other purpose than to help them spear another 2,500 of these things all over the country.
And more so with Labor’s ‘Electricity’ Bill Shorten crowing louder than ever about a ludicrous 50% RET, the number would need to be in the order of 10-12,000 of them. Never mind the cost; and never mind what happens to the stability of the grid.
As Andrew Dodson points out, grid stability (frequency and load balancing) matters. Back in 2012, Australia’s Paul Miskelly (another highly experienced Electrical Engineer) ripped into the patent nonsense of wind power in his paper Wind Farms in Eastern Australia – Recent Lessons – published in the journal, Energy and the Environment. On the risk to grid stability from attempting to integrate intermittent and highly variable wind power output into Australia’s Eastern grid, Paul wrote:
PROPERTIES OF ELECTRICITY GRIDS
On an electricity grid supply and demand must be maintained in balance on a second-by-second basis (AEMO, ). Kirby et al , for example, in discussing these fundamental concepts, state:
“Small mismatches between generation and load result in small frequency deviations. Small shifts in frequency do not degrade reliability or markets efficiency although large shifts can damage equipment, degrade load performance, and interfere with system protection schemes which may ultimately lead to system collapse.”
Bevrani et al  discuss control parameters and strategies in detail and stress that any degradation of electricity grid control system safety margins will result in frequent, unscheduled, widespread blackouts (“system collapse”). A recent German government report highlights the likely catastrophic consequences resulting from any such event.
In South Australia, wind power output fluctuations (rapid surges and precipitous collapses) mean that “the [massive] mismatches between generation and load result in [huge] frequency deviations” – with “widespread blackouts”; which has “degraded load performance”, and led to a dangerously unstable power supply.
STT’s operatives inform us that the wide range in supply voltage caused by wind fluctuations has seen the grid managers in SA (SA Power Networks) reduce the voltage running in the grid to 220 Volts (the Australian Standard is 240). Ordinarily, the system is set to operate at 230 Volts, allowing for normal – load driven – fluctuations above and below that level, such that the upper limit never exceeds 240. Surges above 240 Volts put appliances (especially electronics) at risk of permanent damage. Now, with massive wind power surges a daily feature of SA’s power supply, the grid operator is faced with frequent and rapid rises in voltage; and has adjusted the operating voltage downwards to accommodate it.
So far, so technical. But what really matters is having power whenever and wherever you need it. As Joni Mitchell pondered in her 1970 hippy-hit-classic, Big Yellow Taxi, ‘Don’t it always seem to go, That you don’t know what you’ve got ‘Till it’s gone’.
One day soon, the politicians that put South Australia on the map (for all the wrong reasons) and the useful idiots in the media that helped them, will be arguing where it all went wrong, while sitting freezing (or boiling) in the dark. Welcome to your wind powered future!