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Generally, high-temperature superconducting coated conductors (CC) are hard to be quenched by local and transient disturbances during normal operation because of the high temperature margin and high heat capacity of the conductor. However, the CCs still have possibilities of unexpected quenches originated by the appearance of local defects due to repeated mechanical stresses, and by temperature rise of the long part of the CCs due to malfunction of the cryogenic system, for example. In this work, the hot spot temperature of a CC with copper stabilizer during quench protection sequence is calculated by a numerical analysis for quenches by both of the origins mentioned above. The practical amount of the stabilizer is discussed not to over-protect but for a coil system to surely survive from sever damages caused by quenches considering quench origins.

Two preliminary design concepts for the low T-C. superconductor Toroidal Field coil system of the planned European fusion reactor DEMO were proposed in 2012 by EPFL-CRPP PSI Villigen and ENEA Frascati. The coil consists of eight double layers (DLs) wound using: a) flat multistage cables with two side cooling channels (CRPP design) or b) rectangular CICC with a central cooling channel (ENEA design). The present study is focused on the thermal-hydraulic analysis of the candidate conductor designs, namely: i) hydraulic analysis-calculation of the mass flow rates in each conductor at the expected value of pressure drop in the coil at operating conditions, ii) heat removal analysis-calculation of mass flow rates and the helium outlet temperatures in each conductor as functions of the heat deposition rate, iii) assessment of the hot spot temperature and the maximum pressure in each conductor during quench. The results of our analysis provide the information for further improvement and optimization of the conductors' design.

Oil-filled power transformers are some of the most critical components of the electrical export system for Offshore Wind Power Plants (OWPPs). During contingency situations, dynamic loading of the export transformers becomes essential for debottlenecking and optimization of OWPPs, which is elaborated using a case study of Anholt offshore windfarm export system power transformers. Power transformers can be dynamically loaded if the temporal development of temperatures is known,especially Top-Oil (TOT) and Hot-Spot (HST) temperatures. Since the fibre-optic sensors for direct HST measurements are unavailable and the associated costs are high, these temperatures must be estimated using thermoelectric models based on differential-equations for real-time dynamic loading operation of transformers.The renowned and industry-wide accepted thermal model of IEEE loading guide C57.91 is presented in this paper, along with the recently established but well proven model by Susa et al. Both these models are validated using the instantaneous TOT measurements for one of the 140 MVA, 225kV/33 kV transformers in the Danish Anholt windfarm for the entire 2017 period. The model that is found to perform better is then used for HST calculation for the transformer and the thermal aging of its paper insulation is assessed based on its loading and ambient conditions history for 2017. Furthermore, the thermal utilization and insulation loss-of-life (LOL) based on HST variation of the Anholt windfarm transformer is assessed for increased wind energy generation for 1 year. This is done by upscaling the actual instantaneous load of the test transformer for the entire period of 2017. The upscaling factor ‘W’ is varied over the range of 1.0 to 1.6 pu with the actual instantaneous wind generation in 2017 at Anholt as base. The results are then used to provide insights into transformer dimensioning for offshore windfarm applications and to assess whether the transformer allows further wind energy integration in the existing export system for the Anholt offshore windfarm.