These datasets reflect two main scenarios (S1-S2) associated to the operation of a sandboxing use case SUC3 corresponding to cyber attacks affecting the differential protection scheme of a HV transformer. Details about are illustrated in Section 1.3 of the supporting document. These scenarios analyse the operation of the digital twin of the IEEE 9-bus system and the differential protection scheme under healthy conditions, cyber-attack on communication channels of IEC 61850 Sample Values (SVs) protocol, and a fault in HV side of a transformer in the power system. The scenarios are presented with selected time-series plots in Section 1.3, accompanied a detailed analysis of the processes included and an impact assessment. Thus, during execution of each scenario, data such as electrical measurements were captured and are collected in the form of the datasets presented here. Specifically, SUC3/S1 Differential protection operation during transformer fault corresponds to the dataset of first scenario (S1) of the third sandboxing use case (SUC3) of the KIOS CoE Sandboxing for cyber-physical analysis of EPES, which examines the operation of differential protection scheme (implemented in Typhoon controller) for a HV/MV transformer. The protection scheme receives data sent through IEC 61850 SVs from the two sides of the transformer. Specifically, this dataset corresponds to the first scenario (S1) of SUC3, where a short-circuit occurred on the HV side of a HV/MV transformer of the system. More details about the scenario related to this dataset can be found in Section 1.3.1 of the supporting document. This dataset includes electrical measurements of the current flow, in RMS and sinusoidal format, from the HV and MV sides of HV/MV transformer of the digital twin of the IEEE 9-bus system. The dataset is provided in the form of time-series measurements available as MATLAB (.mat) and CSV files which were recorded with a 30-second and 40-second time resolution, respectively. The measurements of RMS values were recorded by the Typhoon controller, while the sinusoidal measurements were recorder by OPAL-RT. SUC3/S2 MITM with FDI cyber-attack in the SVs of HV transformer side corresponds to the dataset of the second scanario (S2) of the third sandboxing use case (SUC3) of the KIOS CoE Sandboxing for cyber-physical analysis of EPES, which examines a MITM with FDI cyber-attack is conducted on the measurements of the HV side of the transformer, virtually implemented within the sandboxing, and introduces a multiplicative change to the current measurements before they are received by the differential protection scheme via IEC 61850 protocol. Section 1.3.1 of the supporting document provides more details about the scenario related to thisdataset. This dataset includes electrical measurements of the current flow, in RMS and sinusoidal format, from the HV and MV sides of HV/MV transformer of the digital twin of the IEEE 9-bus system. The dataset is provided in the form of time-series measurements available as MATLAB (.mat) and CSV files which were recorded with a 30-second and 40-second time resolution, respectively. The measurements of RMS values were recorded by the Typhoon controller, while the measurements from the sine waves were recorder by OPAL-RT.