By Phil Kreveld, Power Parameters
Irrespective of politics and irrespective of the degree to which Australia might adhere to the spirit of the Paris COP (Conference of the Parties) agreements now and in the future, a perfect storm is brewing in electricity distribution. The obvious reason is that, irrespective of more solar and wind farms in the nation’s high voltage grids, it is in the distribution networks that rooftop solar, whether commercial or privately owned, and charging stations for the electric vehicles are inserted. The latter have little or no impact at the moment but obviously the growth in electric vehicles will see very high, power demand fluctuations. Unsurprisingly, the political debates regarding thermal and hydro base load versus green energy sources bypasses the distribution challenges that are in prospect. Equally unsurprising is the reluctance for investment in upgrading distribution networks in light of strict rules to prevent ‘gold-plating’.
The prospect of upgrading distribution networks raises the challenge of significant capital expenditure in areas such as upgrading conductors to avoid congestion, voltage controls and changes to protection measures. This is a daunting prospect and it is fair to say that such plans are basically shelved for now. However, the steady growth in solar photovoltaic (PV) generation and the future growth in charging stations, particularly fast charging, will cause very great voltage and stability problems and these problems may well force upgrades of physical assets.
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Rather than letting the problems mentioned simply creep up, some countries, for example, the UK, have revised or are revising their distribution grid codes to reflect the new realities. The UK grid code of April 2019 imposes very strict voltage, reactive var, and stability conditions at substation level. This is for Australian eyes, a surprising new regime. In our country of ‘fair dinkum’ power generation concerns, eyes are fixed on the risks imposed by diminishing the fraction of rotational inertia sources in relation to total power demand. It is not argued here that less rotational inertia is of no concern. On the contrary, engineering considerations need to take this into account. In practice we have already seen enforced installation of synchronous condensers for renewable plant in remote zones and the need from time to time for frequency support by frequency control ancillary services (FCAS) generators.
What now appears as urgent is the re-examination of distribution network topologies from substations to fringe of networks in view of a virtually unstoppable insertion of more and more distributed generation and electric vehicle chargers. Rather than tipping out the baby along with the bathwater, it may well be a far more practical for distribution organisations to comprehensively examine power flow, impedance levels in feeders, voltage regulation and stability throughout their networks, to gather this date and to use the information thus gathered for identifying sections that might be compromised in the future. The cost of such studies as suggested here is likely to be a miniscule fraction of potential re-engineering cost involved in network upgrades and minimise upgrades. Furthermore, there is a large degree of ‘future-proofing’ prospects available through such studies. Irrespective of grid code changes in other countries, we should also foresee far stricter regimes being imposed by the Australian Energy Market Operator (AEMO) as Australia transitions to a larger proportion of non-dispatchable generation. Overall stability will, it can be predicted, become an integral part of distribution network responsibility.
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