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What caused the Black System in South Australia


 
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Dr Barry Manor, Sustainability Consultant, explains how the black system occurred in South Australia, creating a loss of electricity for the whole state. On the 28th September 2016 the South Australian electricity grid suffered what is known as a black system. This happens when an entire grid goes down to zero volts, completely losing all electricity.

Amid a period of high winds, lashing rain and thousands of lightning strikes right across the state, this is how the black system happened:
1 There was a fault in the first high voltage line and attempts to reset it failed so it was out of service.
2 The second transmission line also had a fault. Pylons had blown over and the wires were touching the ground, causing short circuits that tripped circuit breakers on the line.
3 120 megawatts of wind power suddenly fell away.
4 A fault occurred on a third segment of transmission line, meaning three high voltage lines were out of service at the same time.
5 Another 192 megawatts of wind power disappeared.
6 The Haywood interconnector between Victoria and South Australia went way above its limits on the amount of current it could carry so its automatic protection mechanisms tripped it off.
7 The Torrens Island and other power stations in the state also tripped off from this current overload.

Those events resulted in loss of power for the state, a black system. Only 8 seconds elapsed from the Step 2 fault to the black system
.

The wind turbines are programmed to constantly monitor the frequency of the voltage in the system, set at 50 hertz (Hz). If the frequency falls below 49 Hz or the voltage drops, the turbines can “ride through” for a short period.
However, they’re set to drop their output if a certain number of faults occur within a defined time period, to avoid damaging themselves and other parts of the grid. On this occasion the transmission line frequency and voltage experienced a sustained drop, triggering the wind power dropout.



 

 
ABC News: Tom Fedorowytsch

The Australian Energy Marketing Operator (AEMO) is now considering changing its protocols for how turbines respond in those conditions. Wind turbines are known as asynchronous generators, because they produce direct current (DC) and convert this to an alternating current (AC) output. This is governed electronically at a frequency of 50 Hz, no matter how fast the turbine is spinning. In contrast, coal-fired power stations are synchronous generators – they maintain a 50 Hz line frequency by directly governing the speed at which the generator is turning. Safeguards in the system serve to prevent substations being overloaded and generators destroyed. Wind turbines use blade feathering (changing the angle of the blades) in high wind to slow them down and prevent mechanical self-destruction. 

The system in South Australia and the interconnector all have safeguards, which contributed to the black system. Load shedding (intentionally enforced blackouts in particular areas or facilities) is another safeguard when there is too much strain placed on the system. Load shedding stops the whole system from going down, but it was not put into practice during the black system event. 
   
There is a constant engineering challenge to match the generation of electricity with the demand for it in real time. Regulating an entire energy system at a state or national level requires some smart engineering and it is unfair and unfounded to blame a system event entirely on renewable energy. 
AEMO has done a thorough investigation of this black system and employed a Canadian engineering consultancy to do an independent report. This confirmed that AEMO’s research was very thorough and that its conclusions were reasonable and well informed. The black system was primarily caused by high winds physically damaging or destroying around 22 transmission line towers, and various protection mechanisms activating to avoid further damage to the network and generators.
    
South Australia is now moving to install battery storage to reduce the intermittency of renewable energy. This will help provide the minimum amount of energy needed to power the state 24/7. Dr Manor believes the way forward is to mandate that any renewable energy source comes with some kind of storage to smooth out intermittent energy over a 24 hour cycle. Storage should also be mandated for any existing renewable energy facilities so the energy is available when it’s needed.

When South Australia had its black system, some people blamed the weather. Comments from senior politicians and the ABC blamed renewable energy. From the facts it is clear that the weather was mostly responsible but that doesn’t stop people playing power politics. 

Dr Barry Manor was interviewed by Ruby Vincet for A Question of Balance, Summary text by Victor Barry 
(amended B Manor 2 April 2017). 


 
Did You Know? The Hazelwood power station that runs on brown coal in Victoria closed at the end of March 2017. Brown coal has a high moisture content so a lot of energy is wasted driving that moisture off the coal before it can be used as a fuel to make steam. Hazelwood has been billed as the most polluting power station in the world. At peak operation, it used around 55,000 tons of coal in 24 hours! Pumped hydro is another form of storage for catering to peak energy demand. Electricity is used to pump water up to high-level dams during low demand periods. The water is then released to produce hydro power during peak demand. Another form of electricity generation with storage is concentrated solar thermal generation. Thermal energy from the sun is concentrated by an array of tracking mirrors (heliostats) to melt specially formulated salts, which can be stored in liquid form in insulated reservoirs. The molten salts are used to generate steam, which spins a turbine generator. A concentrating solar thermal facility has been operating for several years in Spain and Australia is currently building a pilot plant.

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