Cora Petino

Experimental study of a helical coil operating mechanism for future switchgear applications

A key challenge for future switching technologies, especially in the context of the substitution of the strong greenhouse gas sulphur hexafluoride and the ongoing development of DC grids, is the increase of the contact opening velocity within switching devices. Thus, in this contribution a compact helical coil operating mechanism is developed and first experimental investigations are performed to characterize the accelerating and breaking performance of the mechanism. The helical coil arrangement is supplied by currents up to values of several kilo-amperes and the movement of the mechanism is analyzed.

Analysis of the behavior of HVDC converter based on full-bridge submodules during DC fault conditions

The modular multilevel converters are vulnerable to DC side faults, which are severe that can destruct the system if it is not designed to withstand these kinds of faults. This paper presents an analysis of the HVDC modular multilevel converter (MMC) based on full-bridge submodules during DC side fault conditions. A detailed theoretical analysis of the behavior of the full-bridge MMC during fault conditions has been done. Despite the similarity in the operation of the half-bridge and full-bridge modular multilevel converters in normal operation, the MMC based on full-bridge submodules behaves differently in case of fault occurrence, since it has the ability to interrupt the current. The analysis has been verified by presenting the simulation results of a DC transmission system.

Distance protection for HVDC transmission lines based on MMC modulation strategy

In case of permanent pole-to-ground line faults bipolar High-Voltage Direct Current (HVDC) transmission systems can be kept in operation as asymmetrical monopoles. However, power transmission is limited to half of the systems rated power during that time. To reestablish bipolar operation maintenance measures are needed, which can only be performed, if the fault location is known. Within this paper, a new distance protection concept for HVDC systems based on full-bridge modular multi-level converter (MMC) modulation strategy is introduced. An enhanced converter control is used to evoke an alternating current (AC) component on the faulted pole enabling the evaluation of a reactive line loop impedance component. By that, the distance to the fault location can be estimated. The developed concept is applied in a PSCAD model and different fault scenarios are investigated. As the results indicate, the developed concept can successfully be used to localize HVDC transmission system faults, before the faulted line segment is isolated from the rest of the system. Thereby, the proposed technique does not require a communication infrastructure or high sampling frequencies.