AEMO releases final report into SA blackout, blames wind farm settings for state-wide power failure

AEMO releases final report into SA blackout, blames wind farm settings for state-wide power failure


How the weather event tripped the system

On Wednesday September 28, two tornadoes with wind speeds between 190 and 260 kilometres per hour tore through a single-circuit 275-kilovolts transmission line and a double-circuit 275kV transmission line, about 170km apart.
The damage to these three transmission lines caused them to trip, and a sequence of faults in quick succession resulted in six voltage dips on the SA grid over a two-minute period at about 4:16pm.
As the number of faults on the transmission network grew, nine wind farms in the mid-north of SA exhibited a sustained reduction in power as a protection feature activated.
For most of them, the protection settings allowed the wind turbines to withstand a pre-set number of voltage dips within a two-minute period.

When the protection feature kicked in, the output of those wind farms fell by 456 megawatts over a period of less than seven seconds.

When the wind farms unexpectedly reduced their output, the Heywood Interconnector from Victoria tried to make up the shortfall.
About 700 milliseconds after the last wind farm powered down, the flow in the interconnector reached such a level that it activated a special protection scheme that tripped it offline.
The sudden loss of power flows across the interconnector sent the frequency in the SA grid plummeting.
South Australia has an automatic load-shedding system designed to kick-in in just such an event.
But the rate of change of the frequency was so rapid, the automatic load-shedding scheme did not work.
Without it, the remaining generation was much less than the connected load, and as a result, the entire system collapsed.
The SA power system then became separated from the rest of the national grid.
AEMO said its "analysis shows that following system separation, frequency collapse and the consequent black system was inevitable".

http://www.abc.net.au/news/2017-03-28/wind-farm-settings-to-blame-for-sa-blackout-aemo-says/8389920

The Advantages of Ultracapacitors in Wind Turbine Electric Pitch Control Systems

Pitch control systems are used to help prevent mechanical stress to the wind turbine by continuously adjusting the blade pitch in line with the operation strategy of the wind turbine. This not only ensures constant power output of the wind turbine, but also reduces mechanical stress to the turbine structure, extending its service life.

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As we all know, power supply can fail. If the energy grid happens to fail, the turbines need an emergency backup plan. That backup plan is an energy storage system that provides enough energy to return the turbine blades to a neutral position for safe shutdown, which prevents severe damage or total loss of the wind turbine due to strong and uneven wind forces. Ultracapacitors provide these top five advantages over batteries when used as the energy storage system for wind pitch control.

1. High power density = burst power
Unlike batteries, ultracapacitors provide the burst of energy that is needed to return the turbine blades to a neutral position in the event of a grid power failure. They charge faster than batteries and are highly reliable for short-term mismatches between power demand and power availability.

2. Lower total-cost-of-ownership
The upfront cost for an ultracapacitor-based electric pitch control system is the same as a battery-based system. However, the cost for the electrical system (excluding the energy storage device) is more costly for a battery-based pitch control system because batteries require more complex charging and monitoring systems. An ultracapacitor-based system requires fewer components and simpler mechanical mounting and vibration damping than batteries.

3. Long service life and predictable aging
On average, ultracapacitor life span is 12 years under normal operating conditions. This is largely credited to two main factors: the ultracapacitor’s ability to perform in a wide operating temperature range of –40°C to 65°C and an impressive typical cycle life of 500,000 to 1 million charge/discharge cycles.* It’s not uncommon for ultracapacitors to operate with an efficiency of 97% and higher. Unlike ultracapacitors, batteries have a narrow operating temperature range. Harsh environmental conditions and continuous cycling takes a heavy toll on batteries, and they often need replacement every two to four years.

4. No heating or cooling costs
As mentioned above, batteries are vulnerable to the extreme temperatures that ultracapacitors can endure. Batteries require heating and cooling systems, so it’s inevitable that your design cost for a battery-based system is going to be higher. Ultracapacitors eliminate the need for these extra, high-maintenance systems.

5. Light weight
Battery-based energy storage often has to be oversized to accommodate peak power demand—even if this demand occurs only for a few seconds. As a result, battery-based systems are bulkier and weigh more. Ultracapacitors are significantly lighter, and because they have no problem providing burst power during peak power demand, they don’t require oversizing efforts.

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To put this all into perspective, let’s consider an offshore wind farm. It’s an arduous process to send a repair person out to an isolated offshore wind farm for battery maintenance. Considering the advantages of ultracapacitors, wind farm owners and operators can save a lot of time and money by designing in the ultracapacitor from day one.

In the long run, batteries will rack up maintenance and replacement costs that ultracapacitors can almost completely eliminate.

http://www.maxwell.com/blog/advantages-ultracapacitors-wind-turbine-systems

I trust some one in the organisation picked up the phone.

Raider