<p>Distribution grid companies and distribution system operators (DSOs) still mostly follow a traditional framework for grid planning. Such frameworks have so far served DSOs well in the economic assessment and cost-benefit analysis of passive measures, such as grid reinforcement. However, the development towards active distribution grids requires DSOs to also be able to assess an extended set of active measures. To this aim, this paper extends and implements a general planning framework for active distribution grids that builds upon the well-proven traditional framework. The methodology integrated in the framework includes: 1) decoupled models for i) operation with active measures and ii) optimal grid investment, and 2) methods for economic assessment considering active measures from both i) a DSO cost-benefit analysis perspective and ii) a willingness-to-pay perspective. In this paper, operational models are integrated for two examples of active measures, namely the use of fast-charging stations (FCS) and local energy communities (LEC). The methodology is demonstrated in a long-term grid planning case study for a realistic Norwegian medium voltage distribution system. For this case, grid planning with FCS as an active measure reduces the present value of grid investment costs by 70% compared with a passive grid planning strategy. The results also demonstrate how the methodology can be used in negotiating the price of active measures between the DSO and distribution system actors such as LEC and FCS operators.</p>

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Electric vehicles (EV) are by many seen as an integral part of the transformation to a green economy, and are thus expected to increase in number. The charging of EVs is a new challenge to distribution networks and the possible impact of EV charging has recently come to the attention of network companies. This paper presents high resolution measurements of the network impact from EVs during slow and fast charging and some conclusions based on what the measurements indicates.

Abstract-The MgB 2 superconductor is an attractive choice for many high-current DC applications, particularly for its low cost compared to e.g. YBCO, and the higher operating temperature than the low-temperature superconductors. To extend the operating range to include also AC applications, the AC losses need to be determined and a path towards a low-loss conductor needs to be established and verified. To accomplish this development, systematic and reliable measurements of the losses are essential. In this paper we present AC loss measurement results on non-twisted MgB 2 wires with titanium and coppernickel matrices. 50 Hz AC losses were measured calorimetrically in applied magnetic fields, with transport currents, and with combinations of both. The temperature range was between 25 K and T c , the magnetic field was varied up to 300 mT, and the transport current up to 113 A. The measurement results are used as a basis to discuss the necessary AC loss reduction steps in MgB 2 superconductors. 

SF 6 -gas is widely used in medium and high voltage switchgear today because of its excellent insulation and current interruption capabilities. However, due to its high global warming potential, there is a political pressure to replace it wherever possible, resulting in a need for new solutions in the design of compact lowcost switchgear. An evident response is to review and further develop the technologies that were promising before the entry of SF 6 . One of these was the application of gas-emitting insulation materials, in a process of ablation. This paper reviews the range of commercial breaker designs that have taken advantage of ablation in the interruption process from the 1930s until today. The main designs and developments are outlined and some important parameters are explained, such as the steady state ablation-dominated arc, arc quenching and dielectric recovery in the presence of ablation material. The ratings of the mentioned products, as well as more recent experiments, indicate that there is a design limit for simple ablation-assisted breakers at around 20 kV, but the reasons for the apparent limit are not thoroughly studied or explained. Reviving the knowledge of ablation breakers, and combining this with new knowledge and new tools could prove valuable to the development of SF 6 -free MV switchgear.

MgB 2 multi-filamentary superconductors are widely considered for use in dc applications. To expand the possible application range to ac apparatuses, the development of a low ac loss wire is needed. This development involves several steps, and a solid understanding of the loss mechanisms is important to optimize that process as well as for evaluating dc wires exposed to current or magnetic field ripple. In this study we discuss the coupling currents and their influence on hysteresis loss as well as on coupling current loss. We give a phenomenological explanation of the origin and behaviour of the coupling currents and describe the loss patterns for hysteresis loss and coupling current loss separately. Finally, we interpret measured AC losses in an MgB 2 wire cut into different lengths representing different twist pitches. Under certain circumstances short sample lengths are shown to give inaccurate measurement results. On the other hand, short sample lengths of non-twisted wires can be used to estimate the twist pitch necessary to electromagnetically decouple the superconducting filaments.

Inexpensive superconducting wires with low AC losses would open up for a large superconductor market in AC electrical power applications. One candidate for this market is the MgB2 conductor. In the development of an AC optimized superconductor, high-quality measurements of the AC losses under application-like conditions must be available. This article describes an apparatus built for this purpose. The measurement method is calorimetric. The temperature increase of the superconductor sample is measured and compared to the temperature increase due to a heater with known heat input. The system is designed for measurements at temperatures down to 20 K, and for magnetic field strengths up to 1 T (peak) combined with transport currents up to several hundred amperes. Results from tests verifying the capabilities of the system are given, as well as from initial AC loss measurements on a tape-shaped MgB2 superconductor.

Abstract-Ablation-assisted current interruption is a candidate for improving interruption capability in medium voltage switchgear. In high voltage switchgear, ablation is utilized to achieve high pressures in self-blast circuit breakers. Self-blast switch technology adapted to medium voltage could represent an attractive alternative to SF6 technology in load current interruption. However, the arc energies involved would be much lower than in fault current interruption, where self-blast technology is traditionally employed, and to achieve sufficient pressure buildup, this must be compensated for. Higher pressure could be achieved by reducing the radius or increasing the length of the nozzle throat, reducing the heating volume size, changing or increasing the amount of ablative material, or restricting the outward gas flow. Interruption experiments in air have been performed on four different model switch designs that are meant to highlight the possibilities and challenges of adapting self-blast technology to medium voltage load current interruption. The results show that typical load currents can be interrupted at 24 kV, but below a certain critical current, in the present case 200 A, interruptions fail. Self-blast technology could prove useful in medium voltage load current interruption in the future, provided a method for interrupting the lowest currents can be found.