Grid-forming converters are attracting attention for their significant advantages in terms of stability in a weak grid and simulated inertia. However, while they offer great flexibility due to the use of power semiconductors, they are also affected by their low current-carrying capacity. This means that during a fault, instead of the usual voltage control, a current limiting control is active, which changes the dynamic performance of the converter and influences transient stability. This manuscript focuses on the dynamic performance of grid-forming converters during the restart phase at the post-fault period, and proposes an initial phase threshold to prevent the converter from going into current saturation. Based on this, the manuscript proposes several restart strategies during the post-fault period, by using some fast resynchronization methods in order to meet the requirements of the converter’s stable operation and fast active power restoration. Finally, the above findings and the proposed strategies are validated by a joint control hardware-in-the-loop system.

The ban on the use of the greenhouse gas SF ₆ as an insulating and extinguishing gas in equipment and switchgear under the EU’s F‑Gas Regulation requires the use of alternative technologies. This article shows the findings of short-cicuit and operational switching tests of the first installed vacuum circuit breaker in the 110-kV grid in Austria. The focus is to assess the performance during the switching operations and the discussion of the occurred phenomena. Transient phenomena can only be recorded with the use of high-bandwidth CR dividers for voltage and fiber-optic sensors for current measurement. The article investigates a symmetrical terminal fault with multiple reignitions in detail and discusses the switching of a no-loaded transformer. All operational switchings including fault clearings are standard conform and offer valuable insights into the dynamic response of the grid. As result the circuit breaker has been successfully commissioned and is now in operation in the 110-kV coupling bay.

The successful integration of renewable energy into existing power grids relies strongly on converter‐based technologies. These converters are often assigned to one of two categories: grid‐following (GFL) or grid‐forming (GFM). While grid operators must ensure that these converters possess the necessary characteristics, they often lack information about the exact control structures employed. This article proposes assessment tools that characterise GFM and GFL behaviour by performing time‐domain simulations and evaluating measurements at the accessible point of connection (POC) under different grid disturbances. These approaches involve comparing the performance of different controls with the characteristics of ideal voltage and current sources. The findings demonstrate that the presence of a voltage control is indicated by a voltage magnitude jump, while the synchronisation method, such as a phase‐locked loop (PLL) for GFL or power synchronisation control for GFM, can be identified by applying voltage phase jumps. Moreover, as the grid strength or disturbance levels increase, the distinction between GFL and GFM evidently becomes clearer. This work complements existing grid codes by offering easily implementable methods for validating these essential characteristics.