In order to test protection performance of future multi-terminal HVDC grids where DC circuit breakers (DC CBs) play an important role, a DC CB model in real time test environment should be developed. It is well known that a DC CB needs to interrupt DC faults very quickly in order to avoid converter damages and to ensure security of supply. The total current interruption time consists of a fault detection time, which is needed for the DC protection to provide a trip command to the DC CB, and a DC CB interruption time. Thus, it is necessary to demonstrate the performance of associated protective devices through real time simulations, before these devices can be implemented and commissioned in practice. This paper presents a detailed modeling of the voltage source converter assisted resonant current DC circuit breaker (VARC DC CB) in real time simulation environment based on RTDS. The proposed model provides sufficient representation of the circuit breaker for system level studies. External current-voltage characteristics of the proposed VARC DC CB models replicate the ones of the device in the real world. The proposed model of the breaker is tested in a simple test circuit including a DC voltage source and a T-scheme HVDC cable. Additionally, a case study has been presented by making use of a protection algorithm in a multi-terminal HVDC grid with frequency dependent parameters of the HVDC cables to show both protection performance and current interruption.

This paper deals with the modeling, hardware results and model validation by measurements of a VSC assisted resonant current (VARC) dc circuit breaker (CB) and the application within a future network by simulation. The newly emerging VARC dc CB can be used as a solution for the protection of offshore multi-terminal HVDC (MTDC) grids. In this paper, the proposed VARC dc CB is modeled in detail in a PSCAD environment, by taking into account dielectric strength of the vacuum gap, high-frequency current quenching ability and parasitic components. The PSCAD-model is then verified by data from the testing of a 27 kV VARC dc CB prototype with maximum current interruption capability of 10 kA. Additionally, the initial transient interruption voltage and current slope at zero-crossing during the interruption are analyzed. With respect to scaling to a higher voltage level, three types of series connected modules are presented and the performances are compared. The performance of the series connected modules is simulated in a model of a 4-terminal HVDC grid. The obtained results validate the VARC dc CB as a promising solution for the dc fault isolation in MTDC grids.

The main goal of the paper is the modeling of the mechanical circuit breaker (MCB) that can replicate the breaker characteristics in real time environment. The proposed MCB with active current injection is modelled for a system level, which provides adequate representation of the circuit breakers for system analysis studies. External current-voltage characteristics of the proposed MCB models replicate the ones of the devices in the real world. It is well known that the DC circuit breaker (DCCB) needs to interrupt DC faults very quickly in order to avoid converter damages. The total current interruption time consists of fault detection time, time needed for the DC protection to provide command to the DCCB, and DCCB arc clearing time. Thus, it is necessary to demonstrate the system performance of associated protective devices through real time simulation, before these devices can be implemented and commissioned in practice. This paper presents a detailed modeling of the mechanical DCCB in real time simulation environment based on RTDS. The performance of the model is verified by the simulations based on PSCAD and meaningful conclusions are drawn.

The main goal of the paper is the modelling of the mechanical direct current circuit breaker (DC CB) with active current injection that includes different circuit breaker characteristics. System level models provide adequate representation of the circuit breakers for system analysis studies. The performance characteristics of the DC CB in those proposed models replicate the ones of the devices in practice. The developed mechanical circuit breaker model is realized for a 320 kV demonstration circuit in PSCAD environment and its limitations and robustness are analyzed. The performance of the model is investigated by different cases. The obtained results show that the DC CB model can be used with full success for both to simulate DC fault interruptions and to be used for different protection studies.