Improving interruption performance of mechanical circuit breakers by controlling pre‐current‐zero wave shape

Abstract

Mechanical circuit breakers (MCBs) are the limiting component for current injection HVDC circuit breakers. Improving their interruption performance reduces requirements for capacitance and inductance needed in the injection circuit and thus space use and costs. Higher performance can be achieved by creating a period of low current gradient before zero crossing in the MCB, e.g. by using a saturable inductor (SI). In this paper, the impact of duration and steepness during the low currentgradient 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 SI can be derived from arc time constant and interruption limits for constant current gradients. This optimisation results in a considerable increase of interruption performance. The feasibility of implementing an SI in a full-scale HVDC circuit breaker is demonstrated using simulations. Using an improved injection scheme, the stresses for the MCB can be reduced significantly. Consequently, the injection circuit components can be scaled down, 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.

Current Injection Circuit Breakers for HVDC: Overview on Improved Injection Circuits

“…The time between the start of current injection and zero crossing in the MI is expected to be in the range of hundreds of microseconds. Consequently, dynamic injection typically requires the use of costly high power semiconductor switches (an exception would be the use of saturable inductors [3], [12]). In the following, a number of possible circuits is discussed.…”

“…Another option to influence the injection current amplitude (and period) is to change the inductance. Possible measures are adding a saturable inductor in the NCP [3], [9], [12] or influencing the CCP inductance, either by reconfiguration or by controlling saturation. Saturable inductors are passive devices that have shown promising results.…”

“…Gas circuit breakers offer superior voltage withstand, however they have a lower interruption performance in terms of current and voltage gradient. This issue can be tackled by implementing auxiliary circuits to reduce current and voltage gradients at current zero crossing in the MI [12].…”

Swiss competence center on energy research FURIES - Overview and contributions in the area of power electronics and SmartGrids

“…Consequently, circuit breaker topologies for HVDC networks typically consist of three branches that split the tasks of nominal current conduction, counter voltage build-up and energy absorption. Currently established concepts for HVDC circuit breakers include: (i) Passive oscillation topologies are commonly used for metal return transfer switches [14], [15]; (ii) Current injection topologies [16], [17], where recent prototypes have interrupted peak fault currents of 16 kA without specified voltage (charged capacitor, [18]) and 9.2 kA at 160 kV (coupled inductor, [19]); and (iii) Hybrid breakers, combining mechanical and semiconductor switches [14], [20]. An 80 kV [20] and a 200 kV rated prototype [21] of the hybrid topology have been tested, reaching a peak fault current of 10 kA and 15 kA, respectively.…”

Ablation-Dominated Arcs in CO2 Atmosphere - Part I: Temperature Determination near Current Zero

“…Alternatively, the PTFE as the standard nozzle material in commercial circuit breakers can be replaced by polymers that are transparent, e.g. PMMA [14,15].…”