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NETWORK / 10 / FEBRUARY 2020 way they are procured. The responses of generation plant, to what is a not un- common disturbance to the transmission network, were fundamental to what happened on August 9th. Ever since liber- alisation of the power sector, the ESO and its predecessor have had a role in policing the perfor- mance of large generators con- nected to the system although, according to Ofgem, it was relying on Ørsted to self-certify its plant at Hornsea. Moreover, as was seen on August 9th, the behaviour of DG also has an impact on the system. An important recommendation by Ofgem is that arrangements for ensuring compliance of genera - tion with relevant codes should now be reviewed. What are the key learning points? The August 9th incident was not caused by lack of power generation resources or the vari- ability of wind power. Rather, it concerned the ways in which resources are controlled and the system is operated. By international standards, electricity supply in Britain is very reliable and the event on August 9th was small, largely because LFDD succeeded in preventing the situation from getting a lot worse. However, the impact on rail users in the south-east was significant. One event cannot be taken as a sign of deteriorating system stability or of the complete inadequacy of procedures and conventions that have served us well for many years. However, there is no cause for compla - cency. Britain's supplies of energy need to be progressively decarbonised, the technical characteristics of the electricity system continue to change and the engineering needs to be got right. The costs of the transition need to be kept to a minimum but future electricity users will no doubt expect their supply to be, on average, as reliable as it has been up to now. The power system has already been experiencing a growth in DG from around 7GW in 2009 to more than 37GW to - day but little of this is monitored and controlled. Failure to ad- equately manage the operation of DG represents both a threat to the system and the missing of an opportunity to use the services that DG might provide. The DNOs' readiness to become 'Distribution System Opera - tors' (DSOs) was not shown in a good light by what happened on August 9th and, in respect of monitoring of DG, compares poorly to arrangements that are already in place in other coun - tries. As Ofgem said, "substan- tial improvements are required in DNOs' capabilities if they are to transition towards playing a more active network manage - ment role as DSOs". A major challenge, illus- trated by the behaviour of the wind turbines at Hornsea on August 9th, is represented by the growth in use of power electronics on the system. The overall effect of this is cur - rently not well understood and represents both an opportunity and a threat. The situation is not helped by the confidential - ity that sits around the details of how power electronic convert- ers are controlled and there is a need for research and well-qual- ified people to understand the interactions between different converters on the system. This comes at a time when the UK Government's main research funding agency has decided to cut funding to PhD students working on electricity system issues from its core Centres for Doctoral Training programme. Many of these students would have been expected to join the industry. Delivering a resilient system cost-effectively requires the right mix of operational decisions, control facilities, logistics and assets with the right specifica - tions. Engineering standards, clearly defined roles for the sector's various licence holders and codes for governing the relationships between them are critical to getting both the engineering and the commercial relationships right among so many different actors. Respon- sibilities for ensuring electricity system resilience – preventing, containing and recovering from interruptions to supply arising from disturbances – need to be clarified and applied in a more rigorous way. One particular suggestion by Ofgem is that "it may be necessary to consider standards for assessing explicitly the risk- weighted costs and benefits of securing the system for certain events". While not a new idea, this promises to allow actions by the ESO (and DNOs) to be better targeted but depends on the collection of good data on performance of all parts of the system, something that is not done to anything like the required level today. Ofgem said that various issues uncovered by their inves - tigation into August 9th have given them cause for concern about the way the system is operated. Unlike the investiga - tions of Ørsted and RWE, their investigation of the ESO is continuing and will feed into the review by the department of Business, Energy and Industrial Strategy (BEIS) of arrangements for electricity system govern - ance and system operation. Is that a recognition that existing procedures for regulating the sector are inadequate, or that something has changed beyond just the growth of renewable generation? So soon aŸer the ESO came into being (in April 2019), might we see further major to changes to institutional arrangements for planning and operating Britain's power system? "Ofgem has identified a number of issues with the ESO's existing processes and procedures. These include how the need for frequency management services is identified and the way they are procured" BLACKOUT FINDINGS