Introduction

The dataset captures directional overcurrent (DOC) protection settings for grid and primary transformer sites across UK Power Networks' EPN and SPN areas, along with information on whether relays with load blinding functionality have been commissioned at these locations. This data forms part of export curtailment assessment studies, particularly where transformers with DOC protection are identified as operational constraints due to reverse power flows.

Typically, DOC relays detect excessive currents flowing towards the consumer load (e.g., during faults), when distributed generation feeds power into the network, current flowing in the opposite direction can be misinterpreted by the DOC relays as a fault condition. Modern numerical protection relays can include a 'load blinding' functionality, which is designed to prevent unnecessary tripping under normal levels of reverse power flow by masking the DOC protection element when the voltage-to-current phase relationship corresponds to a typical power factor of ±0.85, indicating non-fault conditions.

By installing load blinding relays at grid and primary sites limited by DOC, reverse power flow exceeding the DOC setting can be tolerated within a defined envelope, ensuring that protection is only triggered by abnormal conditions, such as faults with poor power factor. Load blinding relays increase the limitation from the DOC setting to the continuous rating of the transformer, unless other limitations (e.g., tap changer reverse power flow capability) are breached first, in which case the stringent limitation will be used instead.

UK Power Networks has been providing customers with curtailment estimate assessment using this dataset to model limitations linked to the DOC setting in transformers across EPN and SPN licence areas. In addition, UK Power Networks DSO has initiated a programme of work to commission load blinding relays in constraint locations currently limited by DOC to unlock additional generation capacity.

The dataset includes DOC settings for both grid transformers and primary transformers, if applicable, with limits available in Amps and MVA. It also provides visibility on whether the load blinding relay has been commissioned.

The dataset is regularly updated and maintained to ensure that the DOC settings reflect on-site settings.

Methodological Approach

This section covers the calculation of DOC protection limit in MVA to align with other limits used in curtailment estimates.

All Grid and Primary sites across UK Power Networks’ licence areas that were considered during Distributed Energy Resources Management System (DERMS) scheme design and when producing curtailment estimates were recorded in a dedicated spreadsheet. For each site, the Planning and Protection team was consulted to determine the DOC limitation that applied to each specific grid or primary site. The confirmed values were then cross-checked against internal databases to ensure accuracy.

The dedicated spreadsheet was then used to create a dataset where all DOC values were included. The value in MVA was calculated from Amps using the following formula in a script developed by Network Access team:

Where:

• DOC_Setting_Amp is the current DOC setting in Amperes
• Voltage (kV) is the voltage of the transformer at the low voltage terminal in kV
• DOC_Setting_MVA is the calculated apparent power in MVA

Quality Control Statement

Settings are retrieved from UK Power Networks protection setting database in SAP. Additionally, where required, the UK Power Networks Protections team conducts site visits to ensure the limit matches the configured limit in the respective transformers.

Please note that the data presented in these tables represents the most current information available and reflects our best technical understanding at the time of publication. Despite the rigorous quality control measures outlined above, UK Power Networks cannot guarantee absolute accuracy and does not accept responsibility for any errors, omissions, or operational decisions made based on this data. For any queries or clarification regarding this information, please contact the Network Access team at: networkaccess@ukpowernetworks.co.uk

Assurance Statement

This dataset is generated using a script developed by the Network Access team, which groups the DOC limits provided by the UK Power Networks Protection and Planning teams and validates by calculating the MVA value for all grid and primary transformer sites. This dataset will be reviewed and updated on a weekly basis to account for any changes or completion of load blinding installation work, ensuring that the dataset remains relevant and reflective of the network over time.

Other

Download dataset information: Metadata (JSON)

Definitions of key terms related to this dataset can be found in the Open Data Portal Glossary: https://ukpowernetworks.opendatasoft.com/pages/glossary/