Study of vacuum arc plasma transport characteristics during the DC interrupting process

The mechanical DC vacuum circuit breaker based on forced-over-zero technology will inevitably generate vacuum arc during the actual interrupting process. Since the current drop frequency is usually very high, the vacuum arc usually exhibits obvious transient characteristics, and the excessive transient characteristics may even become a key factor limiting the interruption capacity. In order to improve the mechanical DC vacuum circuit breaker arc interrupting capability, this paper establishes a vacuum arc transient magneto-hydrodynamic simulation model in the DC interrupting process and studies the plasma transport characteristics of the vacuum arc under different DC interrupting conditions. The results show that the ion pressure, ion density and ion temperature decrease with decreasing arc current, while the ion velocity gradually increases during the DC interrupting process. The increase in breaking current and current drop frequency will increase the ion density in the arc column at the moment of current crossing zero, resulting in more difficult vacuum arc interrupting. The results of the study can provide an important theoretical basis for a deeper understanding of the vacuum arc transient process in the DC interrupting process and improve the DC vacuum circuit breaker arc interruption capability.

Rational reconstruction of sectioning posts of AC catenary at disconnectors

Operation of sectioning posts of the AC catenary at the disconnectors on the Gorkovskaya railway for a period of more than 60 years has shown its reliable operation, and the maintenance was reduced to a minimum. However, due to the growth of heavy haul and high-speed traffic on a number of sections, their reconstruction was required. In accordance with the current regulatory documents, such a reconstruction provides for the transfer of the operation of sectioning posts from disconnectors to circuit breakers. In connection with the reliable operation of the sectioning posts on disconnectors and the simplicity of their maintenance, it is proposed to expand the options for the reconstruction of the sectioning posts on the disconnectors and to introduce three reconstruction options into the regulatory documents. The first option provides for the reconstruction of the sectioning post with disconnectors by transferring it to the classic scheme with four switches, as indicated in the current regulatory documents. The second option provides for leaving the sectioning post at the disconnectors, but adding a fast-acting automatic reclosing device in the inter-substation zone in case of passing short circuits. The third option provides for the reconstruction of the sectioning post on disconnectors with the introduction of a vacuum circuit breaker into the bus of the post and a device for high-speed automatic reclosing and opening of the disconnector, in the zone of which a short circuit has occurred. The schemes of automatic devices for determining a stable (passing) short circuit in a traction network and a device for determining the location of damage are considered. The operation of the sectioning posts, reconstructed according to the indicated options, has been tested practically at the existing sections of the power supply of the traction network of the Gorkovskaya railway. All of them have shown high reliability.

Development and Testing of a 252 kV/2500 A-40 kA Multi-Break Bus-Coupler Fast Vacuum Circuit Breaker

It is effective to open the bus-coupler circuit breaker in case of a short-circuit fault. A fast vacuum circuit breaker (FVCB) is an ideal bus-coupler circuit breaker due to its high velocity. The objective of this study was to develop and test a 252 kV/2500 A-40 kA multi-break bus-coupler FVCB. The 252 kV FVCB contained 12 FVCB units. Each phase consisted of four FVCB units connected in series. Each FVCB unit had an electromagnetic repulsion mechanism with an average opening velocity reaching 6.5 m/s. Test results showed the opening time was 1.11 ± 0.08 ms. The capacitance of the voltage grading capacitor of each break was determined to be 10 nF. The prototype 252 kV bus-coupler FVCB passed all partial test duties according to the IEC 62271-100: 2008 and IEC 62271-1: 2007 standards, which include an insulation test and a terminal fault test among others. A 252 kV/2500 A-40 kA multi-break bus-coupler FVCB can be used to quickly cut off a short-circuit fault and effectively limit a short-circuit current.