Tim Schultz


Last Name

Schultz

First Name

Tim

ORCID

0000-0001-7226-2622

Organisational unit

01109 - Lehre Bau, Umwelt und Geomatik

Filters

2015 - 202018
Reset filters

Search Results

Publications 1 - 10 of 18
  • Identification and Improvement of HVDC Circuit Breaker Interruption Limits
    Item type: Doctoral Thesis
    Schultz, Tim (2019)
    High voltage direct current (HVDC) circuit breakers are a key technology, required for the safe and reliable operation of multiterminal HVDC systems. Natural current zero crossings do not exist, consequently rendering the established technologies of AC fault current interruption ineffective. In the recent years, a variety of possible solutions to this task has been suggested. However due to the absence of common standards and established test procedures, it remains difficult to judge their performance. In this thesis, a comparative simulation study on the performance limits of representative HVDC circuit breaker topologies has been performed. Topology dependent performance limits and the ability and required effort to upgrade have been investigated based on synthetic fault currents. A transfer of the implemented models to a multiterminal HVDC grid simulation showed considerable differences between the individual topologies for different fault cases. This supports the assumption that worst-case scenarios are topology dependent and grid related phenomena have to be considered when testing HVDC circuit breakers. In the second part of this thesis, the identified performance limitations of the current injection topology are investigated. Compared to other topologies, it provides low costs and a robust structure making it a promising candidate for the use in HVDC grids. Its performance is defined by the current breaking limits of the mechanical interrupter. While these are established and have been intensely studied for AC, there is a lack of information regarding the interruption limits under typical stresses in current injection HVDC circuit breakers. In the presented thesis, this gap is addressed by tests using a model gas interrupter. Based on a characterization of the interrupter, auxiliary circuits have been developed to reduce current and voltage gradients during a sufficient time around current zero to extend interruption limits. As a result, capacitance and inductance in the injection circuit can be reduced and an overall superior design achieved. The feasibility for the use in HVDC systems has subsequently been evaluated by means of simulation.
  • Swiss Competence Center on Energy Research FURIES - Overview and Contributions in the Area of Power Electronics and SmartGrids
    Item type: Conference Paper
    Favre-Perrod, Patrick; Biela, Jürgen; Carpita, Mauro; et al. (2019)
    2019 21st European Conference on Power Electronics and Applications (EPE '19 ECCE Europe)
    This paper introduces a special session on results of the Swiss competence center on energy research FURIES that has been established in coordination with the Swiss Energy strategy 2050 with the specific aim to develop, promote and deploy power grid-related innovative solutions toward the implementation of the Swiss Energy Strategy 2050. This contribution will report on activities within WP 3, “AC/DC multi-terminal grids and power electronics”. This WP includes three subtasks with contributions from the major Swiss technical universities: Multi-terminal HVDC system design, fault detection and clearing in multi-terminal HVDC, enabling component and converter technologies and applications. The spectrum of the center's activities is briefly introduced and as an illustrative example, the contributions of the SCCER FURIES in relation with HVDC grids are summarized. These contributions include: new high power DC testing methods and laboratories, new DC breaker principles and fault location techniques, AC/DC grid resonance analysis and novel converter technologies.
  • Post-Arc Current Measurement in Mechanical Circuit Breakers for HVDC Applications
    Item type: Journal Article
    Schultz, Tim (2017)
    Plasma Physics and Technology
  • Ion flow simulations of HVDC conductors under rainy conditions
    Item type: Conference Paper
    Schultz, Tim; Pfeiffer, Martin D.; Franck, Christian (2015)
    11th IET International Conference on AC and DC Power Transmission
  • Interruption limits of mechanical circuit breakers and circuit upgrades for current injection in HVDC circuit breakers
    Item type: Journal Article
    Schultz, Tim; Herzog, Patrik; Franck, Christian (2020)
    High Voltage
    Current injection circuit breakers consist of a mechanical interrupter (MI) with a current injection and an energy dissipation branch in parallel. The performance of the complete device is largely determined by mechanical operation time and interruption performance of the MI. In the standard configuration, current injection is realised using a pre-charged inductor– capacitor circuit. A higher interruption performance of the MI makes it possible to scale down the resonant injection circuit, and thus have a more economical design. Additionally, the implementation of more complex injection circuits that quickly create zero crossings, while maintaining favourable conditions for interruption, can lead to economic benefits. In this study, the interruption performance of a model gas interrupter as part of a current injection topology is investigated. The results are used to verify a corresponding simulation model and two-dimensional upgrade circuits that influence the injection current to increase the range of interruptible fault currents. On the basis of experimental results, the simulation model is used to investigate the performance of upgrade circuits for the use in high-voltage direct current (HVDC) systems. The results indicate that using improved injection circuits can considerably increase the economic advantage of current injection circuit breakers compared with other topologies.
  • Explaining the impact of conductor surface type on wet weather HVDC corona characteristics
    Item type: Journal Article
    Schultz, Tim; Pfeiffer, Martin D.; Hedtke, Sören; et al. (2016)
    Journal of Electrostatics
  • Optimierung von Ionenstromsimulationen für HVDC-Leitungen unter regnerischen Bedingungen
    Item type: Conference Poster
    Schultz, Tim; Franck, Christian (2015)
  • Circuit Breakers for Fault Current Interruption in HVDC Grids
    Item type: Conference Paper
    Schultz, Tim; Lenz, Viktor; Franck, Christian (2016)
    ETG-Fachbericht ~ VDE-Hochspannungstechnik 2016: Vorträge der ETG-Fachtagung 14.-16. November 2016 in Berlin
  • Determining the Time Constant of Arcs at Arbitrary Current Levels
    Item type: Conference Paper
    Bort, Lorenz; Schultz, Tim; Franck, Christian (2019)
    Plasma Physics and Technology
  • Improving interruption performance of mechanical circuit breakers by controlling pre-current-zero wave shape
    Item type: Journal Article
    Schultz, Tim; Hammerich, Benjamin; Bort, Lorenz; et al. (2019)
    High Voltage
    Mechanical circuit breakers (MCB) are the limiting component for current injection HVDC circuit breakers. Improving their interruption performance reduces the requirements for capacitance and inductance needed in the injection circuit and thus space use and costs. Higher interruption performance can be achieved by creating a period of low current gradient before zero crossing in the MCB, for example by using a saturable inductor (SI).In this article, the impact of duration and steepness during the low current-gradient phase is linked to arc parameters of the investigated model gas circuit breaker. It is shown in a scaled experimental setup that an optimum design of the saturable inductor can be derived from arc time constant and interruption limits for constant current gradients. This optimization results in a considerable increase of interruption performance.Based on experimental results, the feasibility of implementing a saturable inductor in a full scale HVDC circuit breaker is demonstrated by means of simulation. Using an improved injection scheme, the stresses for the mechanical interrupter can be reduced significantly in terms of rate of rise of current before and voltage after zero crossing. As a result, it is possible to scale down the components of the injection circuit, making the topology more economical. The reduced interruption requirements might also make it possible to use a single gas interrupter instead of a series connection of vacuum interrupters, reducing the complexity of the mechanical switch.
Publications 1 - 10 of 18