Gheorghe Dumitrescu

Investigation of the rotating arc plasma generated in a vacuum circuit breaker

The main goal of this work is a better understanding of the physical phenomena taking place during the high currents interruption process, corresponding to short-circuit regime in the electrical networks. The arc appearance and its behavior in vacuum circuit breakers with cup-shaped electrodes were explored with an adequate optical system. Different current interruption situations were correlated with optical plasma diagnosis. Specific peculiarities of the time resolved spectra recorded in the proximity of the short circuit current zero (c.z.) moments are reported. On this basis the authors attempt to define a set of plasma parameters which are critical for the studied interruption processes and the breaking capability evaluation.

Installation and equipment for the research of the electrical switching arc in advanced vacuum

The paper presents some results obtained by the authors in the manufacture and use of equipment and adjacent measuring and diagnosis devices developed for the research of electrical switching arcs in vacuum. Tests were made for the current range 0.5-30 kA RMS and voltages between 200-1400 V. The evolution of currents and electrical switching voltages related to mechanical and vacuum breaking process parameters was recorded. Diagnosis measurements relatively to the diffuse or constricted state of the breaking electrical arc column were also performed. Research concerning the influence of the additional magnetic field upon the electrical switching arc in a vacuum have also been initiated.

Post-arc current in low-voltage vacuum circuit breaker: Measurements and physical peculiarities

This paper presents the main peculiarities of the post-arc (p.a.) current within the low-voltage switching process in a vacuum as compared with the medium-voltage p.a. current. The high-frequency p.a. current oscillation is measured and mathematically described. There are two high-frequency components produced by the equivalent scheme of the circuit breaker and by the nonlinear characteristic of the p.a. residual plasma. Also described is the influence of the axial magnetic field (AMF) on the p.a. current evolution and high-frequency oscillation. The authors have noticed that the nonlinear p.a. high-frequency component, produced by nonlinear characteristic of residual plasma, is severely damped by the AMF. Using an analytical approach of the phenomenon, this study also provides a general mathematical model for the p.a. current. The results of the mathematical model contribute to a better understanding of the physical peculiarities of the short-circuit current zero zone.

Moving Arc Study and Plasma Diagnosis in Vacuum Interrupters With TMF Contacts

Electrical and optical investigations are focused on a vacuum circuit breaker study. The short-circuit regime in the low-voltage network is exactly reproduced by a specific test circuit. The analysis of the phenomena during the high-current evolution and on the current-zero zone is made for the purpose of increasing the breaking capability of this kind of equipment. The displacement speed of the arc column on the surface of the contact pieces in the case of the transverse magnetic field solution is correlated with the spatial and temporal plasma diagnostic. For post-arc current being an important element defining the quality of the short-circuit interruption process, specific measurements are also performed. For better understanding of the high-current interruption in vacuum, the experimentally studied phenomena are mathematically modeled.

Upon the influence of the post-arc current on the low voltage switching process in vacuum

The paper presents one stage of the scientific research, performed for the investigation of the post-arc (p.a.) current within low voltage switching process in vacuum, when interrupting short-circuit currents of high values. A large power equipment, supplied by the mains and providing an accurate reproduction of the processes, concerning the short circuit phenomenon (U=1.5 kV; I=100 kA) was used. An experimental model, which can reproduce the switching conditions of the power circuit-breaker in vacuum, was available as well. The influence of an axial magnetic field on the p.a. current and the switching process was also explored.

Moving Arc Study and Plasma Diagnosis in the Case of Vacuum Interrupter with TMF Contacts

Electrical and optical investigations are focused for a vacuum circuit breaker study. The short circuit regime in the low voltage network is exactly reproduced by a specific test circuit. The analysis of the phenomena during the high current evolution and for the current zero (c.z) zone are done in the aim of increasing the breaking capability of this kind of equipment. The displacement speed of the arc column on the surface of the contact pieces in the case of transverse magnetic field (TMF) solution is correlated with the spatial and temporal plasma diagnostic. The post-arc current being the main element defining the quality of the short circuit interruption process, specific measurements are also performed. In order to a better understanding of the high current interruption process in vacuum, the experimentally studied phenomena are mathematically modeled

High-current vacuum arcs on magnetic field contacts: electrical, spectroscopic and contact temperature investigations

The paper deals with the electric arc phenomena in a low voltage circuit breaker in order to improve the breaking capability. Electrical and thermal parameters were measured in the high current arc period and in the zero current moment (CZ) and corroborated with the arc plasma spectroscopic investigations. Considerations concerning successful or unsuccessful high current interruption are presented. The paper presents results based on single shot time resolved emission spectroscopy around the CZ.

Post-arc current in low voltage vacuum circuit breaker: measurements and physical peculiarities

Continuing the investigation of the post-arc (p.a.) current within low voltage switching process in vacuum, the high modulation frequency of the p.a. current was also taken into account. The constants fitted for the adopted mathematical simplified p.a. model were deduced from the experimental data, considering an equivalent scheme of the quenching chamber in vacuum formed from a capacitance and the electric discharge in a nonlinear environment.

The process of strong currents interrupting in low voltage vacuum circuit breakers

The paper presents an investigation of the post-arc current within low voltage switching process in vacuum. From the experimental results were deduced the constants fitted for the adopted simplified mathematical one-dimensional post-arc model. By comparison between the experimental and calculated evolution of the post-arc current and transient recovery voltage, in the first /spl mu/s after the current zero moment, one can obtain an efficient tool for predicting the vacuum circuit breaker behavior, or for improving it.

Investigation of the rotating arc plasma generated in transverse magnetic field (TMF) contacts of vacuum interrupter

The present paper deals with the problem of the TMF interruption systems breaking capability concerning vacuum circuit breakers. The main goal is a better understanding of the physical phenomena taking place during the interruption process, for high currents, corresponding to short-circuit regime in the electrical networks. The arc appearance and its behaviour were explored with a dedicafed optical sqstem. An example of spatial and temporal distribution of the arc light intensity is presented. Specific peculiarities of the optical spectra recorded in the proximi@ of the short circuit current zero (C.Z.) moments are reported. Different current interruption situations are correlated with plasma spectral diagnosis. On this basis the authors try to define a set of plasma parameters which are critical in the studied interruption processes.