Magnus Backman

Medium voltage DC vacuum circuit breaker

The increased use of directed current (DC) as an enabler for the integration of renewable sources gains rising interest also for power transmission and distribution networks. Some preliminary installations showed some benefit of this technique compared with alternating current (AC) and pushed the development of switchgear for high (HV) and medium voltage (MV) DC grids. Several techniques able to provide DC interruption have been proposed in publications and are briefly described. The article focusses on actual development activities and tests of a medium voltage DC circuit breaker based upon the concept of current injection using a medium voltage vacuum interrupter.

A new hybrid medium voltage breaker for DC interruption or AC fault current limitation

A hybrid medium voltage breaker consisting of a power electronic switch (PE) by-passed by a parallel mechanical switch is presented in the paper. The main operation modes and the performances of a 12 kV apparatus with 25 kA short-circuit current capability are introduced. The results of the experimental tests confirm the electrical behaviors foreseen by the simulations during the design phase. The uses of the apparatus in MV applications as AC fault current limiter (FCL) and DC circuit breaker are presented and discussed.

DC power distribution: New opportunities and challenges

The benefits offered by the DC energy distribution in different applications raised the interests towards new power architectures and apparatus. The availability of the related LV and MV apparatus and protection schemes is in fact crucial to fully exploit the opportunities opened in the energy management for the smart grid. Experimental results of testing DC circuit breakers based upon current injection and solid-state technologies are presented and their effectiveness for DC distribution protection is discussed. The possibilities opened by local measurement and communication to support the operation of DC circuit breakers for DC protection as well as the design challenges and implementation issues are investigated.