National Grid System Operator (NGSO) has recently published its Winter Outlook for 2019/2020. The document focuses on the expected trends and predicted outputs the GB electricity market is likely to experience during the winter months.
The most significant topic within the Winter Outlook is the upcoming Triad season. The Triad season lasts between November and February and impacts demand customers with half – hourly metered data. Triads are the 3, non-consecutive half-hour settlement periods, occurring at least 10 days apart for which system demand on the GB transmission network is at its highest. The aim of the Triads scheme is to encourage customers with large demand requirements to reduce their usage of the transmission system during peak times.
Triad avoidance has increased within recent years which has involved demand customers switching to distributed generation and onsite generation as well as reducing their energy consumption in order to avoid large TNUoS charges. One of the main types of distributed generation that has been utilised by demand customers is battery energy storage. Winter 2018/19 was the first time where the transmission system experienced frequency deviations during a Triad period. The frequency changes are believed to be accredited to batteries connected to the distribution network switching from charging to discharging to supply the demand for larger capacity customers. Triad avoidance forecasting is expected to be more difficult for winter 2019/20 due to the increase in Battery Storage. During the summer, the transmission system saw abrupt changes in the demand in response to the wholesale electricity market price. These changes are believed to be associated with the switching of battery generators from charging to discharging and are expected to contribute to a greater uncertainty in Triad forecasting.
The Winter Outlook has laid out National Grid SO’s expectations of interconnectors utilisation over the winter months to address system demand. It is forecasted that 5 interconnectors will be used in this way, with 2 interconnectors connecting to the island of Ireland and a further 3 with mainland Europe.
The GB transmission system is expected to be a net importer of electricity from mainland Europe interconnection during winter, with around 3610MW being imported from mainland Europe overnight and also during peak demand times. The interconnections with Ireland are expected to see the GB transmission system exporting around 750MW of electricity during peak demand as well as importing during times of high wind output in Ireland.
The largest value of the imported electricity from mainland Europe is expected to be supplied via the IFA interconnector with France (1670MW), with the BritNed (Netherlands) and Nemo Link (Belgium) each having peak import power of 1000MW. The interconnectors were awarded Capacity Obligations for winter 2019/20 through the Capacity Market auction in 2015.
The document has also highlighted the wider access to the GB Balancing Mechanism (BM) development, which will allow new revenue streams for smaller generators. NGESO have announced the easing of restrictions for generators wishing to connect to the BM. The BM is used by NGESO to ensure the balance of supply and demand for the transmission system for every half-hour period.
The development includes;
- lowering the limit of generation capacity of generators which are applicable to be part of the BM from >100MW to >1MW (allowing for smaller generators to participate as secondary BM units);
- the introduction of a Virtual Lead Party that will be able to register and ultimately have the responsibility of Secondary BM units and also enhance the IT interface between NGESO and participating generators within the GB balancing mechanism. The Wider Access development will also allow smaller generators to participate with the Trans-European Replacement Reserve Exchange.
NGESO set out plans for maintaining voltage and frequency stability during the winter months. These include contracting generators to be energised during times which may have been previously uneconomic, and taking in-day trading actions via the BM to provide reactive power to the system.
The Winter Outlook has also implemented the lessons learned from the recent power outage in August. NGESO, in collaboration with the ENA, have rolled out a plan to update the protection settings of distributed generation which will reduce the need of operational tools to help manage the stability of the system.