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Name of University: The University of Manchester Candidate Name: Melake Kuflom Degree Title: The Degree of Doctor of Philosophy Title: Impact of UK Low Carbon Energy Scenarios on Transmission Network Protection Policies Date: June 2019 Traditional UK power stations operate using synchronous generators which ensures they deliver a high fault level, are the main source of system inertia and provides the control of the power frequency. Recently, the percentage of demand satisfied by large synchronous generators has significantly reduced, as more wind farms, photo voltaic sources, power electronic converters, storage and HVDC links are integrated within the power system. Increasing deployment of converter based generation within the distribution networks and the decline in large scale traditional synchronous power generation at transmission level results in a fault level reduction across Great Britain network and severe implications for the effectiveness of existing protection relaying performance. The reduction in inertia also poses a challenge for power system stabilises, especially following a disturbance such as the tripping of a large synchronous generation or a major interconnector to a region with synchronous generation. This project studies the behaviour of existing protection relaying scheme as related to the future power system protection strategies of Great Britain and to establish how adaptive the relay can be to the future generation mix and changes in summer minimum demand. This project also presents the protection setting strategy used on the existing GB transmission network and to assess the limitation of exiting protection schemes as related to the future protection setting strategy when the source delivers a fault level that changes from a high level (strong source) to a low level (weak source). From the research outcome, the performance of overcurrent protection is the most affected scheme whereas unit protection is the least affected scheme during low fault level conditions. The proposed alternative transmission protection strategies are configuring distance protection with weak infeed logic, overcurrent protection with voltage restraint, and deploy two unit protections as main 1 & 2 with distance protection as backup in condition when distance protection is not suitable. Other recommended scheme includes unblocking distance schemes with weak infeed, wide area protection and travelling wave based protection. This thesis introduces briefly the aim & scope of the project, and then reviews the key papers in the field as well as existing protection schemes as used in the GB transmission system. Following this, a review into fault level, sensitivity of protection schemes, and challenges as related to the future scenarios are discussed. The impact of low fault level on existing protection schemes, alternative protection strategies, overview on the role & impact of IEC61850 protocol for future protection development, and conclusions are provided at the end.