Utility Week

UTILITY WEEK | 28TH FEBRUARY - 5TH MARCH 2020 | 21 Operations & Assets "We're still in a huddle, figuring out what we need to do there." Voltage To maintain voltage at the correct level, the ESO must ensure there is the right amount of reactive power in the right places to push the active power – the useful bit – around the electricity system. The more reactive power, the higher the voltage. Generators can both absorb and produce reactive power. Network assets such as reactors and capacitors currently provide the majority of baseload reactive power requirements. The ESO tops this up through trading with generators, typically buying their active power output to acquire reactive power capa- bilities. Most large generators are obligated to have the ability to provide reactive power services but can only be ordered to do so when they are already running. The ESO also holds six-monthly tenders for providers with enhanced capabilities as well as ad hoc ten- ders when specific needs arise. Reactive power services have historically been provided by transmission-connected fossil fuel power stations dotted around the country, but as these are crowded out by new wind and solar farms o…en connected at the distribution level and concentrated more towards the UK's extremities, the places where they are needed and available are shi…ing. In general, the ESO faces a growing need for reactive power absorption on the trans- mission network because of falling minimum demand and reactive power consumption on distribution networks. With this in mind, the body is trialling a new type of reactive power service. It initially held a shorter one-year tender to cover an immediate requirement for reactive power absorption in the Merseyside region start- ing this April. "With the closure of Fiddler's Ferry, that was the area with the most press- ing need on the system," says Leslie. As with the first phase of the stability pathfinder, the short lead time meant it was only really suitable for existing assets. The results were released in January, with con- tracts awarded to Inovyn and Intergen. A second nine-year tender for the region start- ing in April 2022, which is accessible for new assets, has also been launched. One of the aims of the work stream is to see whether competitive tenders can meet long-term requirements at a lower cost than network assets. Accordingly, the tenders are for reactive power capability only, creating new opportunities for assets that can pro- vide this service while producing little or no active power. Leslie says this includes renew- ables, which are already being tapped by the ESO through other routes. Black start This is the service that would be used by the ESO to reboot the power grid a…er a complete shutdown. Although the ESO has already made reforms to allow renewables to par- ticipate, the process still works from the top down, with the transmission network being energised before distribution networks are reconnected. Most of this capability is currently pro- vided by large fossil fuel power stations connected at the transmission level. Burt describes the service as their "last bastion" in an increasingly decarbonised energy sys- tem. "But because those power stations are going to be operating less in the future, they won't be as warm and there won't be as many of them, and that means they'll be more expensive for us to buy to provide that black start service," he adds. The ESO is developing a new backup plan through an Ofgem-sponsored project called Distributed Restart. This would be a bottom-up process, with a series of power islands being formed on distribution net- works before being merged together. It would allow the increasing volumes of distributed energy resources to participate, including wind and solar farms, batteries and demand- side response. The project is now entering the second of three years. The first year of work focused on evidence gathering and feasibility studies. "The challenge is you've got to start oper- ating the grid with no power at all," he tells Utility Week. "You've got a whole chain of different generators; you've got a really com- plex communications and telecoms process; you need to find a way commercially and regulatorily to make that service attractive to someone who is not really built to provide very secure national services at the moment. "And you've got to find a way to make that viable, not just for the initial contract signature, but so that you know you've got a reliable service in a one in 25-year event, whenever it happens." Burt says the key to success will be con- tinuous trials and rehearsals so that if the system does go down "people don't need to think. They can just do and act and know that things are going to work properly first time". The first field trials of the new service are expected to begin over the summer. KEY MILESTONES source: National Grid Voltage Thermal Stability Frequency Restoration 2020 2021 2022 2023 2024 2025 Faster-acting post-fault response and greater standardisation of reserves Reactive services from non-traditional and embedded providers trial Visibility and control of new distributed energy resources trial Long-term contracts from a range of providers trial Full suite of new response products procured close to real time Stability market launches paying new and existing providers Whole system optimal dispatch trial New market for reactive services Long-term contracts come online trial Loss of mains relay change programme GB restoration standard and implementation Post-fault constraint management services trial Whole system visibility and control of new embedded connections Full suite of new reserve products procured close to real time New reactive only providers (OMW) New stability only providers (OMW) Real-time procurement and dispatch of response First embedded restoration providers come online New response products maintaining pre-fault frequency Services sourced through competitive procurement come online Complete productionisation of Distributed Restart project Barriers removed for all technologies to provide response and reserve Increased efficiency of system operation on a low-inertia system Operational highlights Increasing reduction in generators synced at periods of low demand First low-demand weekends with no additional generators synced First full week during thesummer with no additional machines synced Extended periods of zero-carbon operation First low-demand periods where no extra generators are synced to provide response and/or voltage support

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