The continuing evolution of high voltage circuit breaker technology has directed current research and development throughout the switchgear industry towards the next generation of interrupter devices, which offer even more advantages than currently applied technologies. A novel rotating arc SF₆ filled interrupter designed to interrupt fault currents at the 145kV level is investigated for such an application. Initial low voltage, low current tests examine the magnetic field and phase angle in the arcing volume, identifying a number of solutions which can be utilised to reduce eddy current circulation in the structural components of the rotating arc coil assembly and consequently optimise the spatial distribution in the arcing volume. The structural capability of the interrupter components has been investigated experimentally under short circuit fault conditions. Short time current tests in excess of 70kA have demonstrated that the coil components can fail when the coil is subjected to extremely high thermal and mechanical stresses due to the short circuit fault current. High-speed photography has been utilised to investigate if the rotating arc interrupter is operating as was initially envisaged and identified fundamental properties of the arc during the interruption process as well as provide information regarding the condition of the arcing volume following arc extinction to assess the dielectric integrity of the interrupter. Although measurements identified correct operation of the rotating arc interrupter, a number of problems with the design have been identified during the test series. The initial half cycle of arcing in the core of the arc runner electrode has been investigated experimentally utilising high speed footage and optical fibres fitted directly to the arc runner electrode revealing important characteristics with respect to the rotating arc interrupters performance. Optimisation of the arc transfer time from the fixed contact to the arc runner electrode has been identified to be one of the fundamental parameters in successful operation. The arc's velocity has been measured experimentally as a function of applied peak current and interrupter gas pressure identifying significant variation in the performance during low and high current operation due to deviation in Lorentz force. Dielectric probe and optical pressure measurements have provided direct evidence of the condition of SF¢ gas in the arcing volume and identified problems associated with the capability of the interrupter to remove hot gas and ionised particles. Finally high current, high voltage tests have been performed to ascertain the limits of the interrupter design at 145kV level by simulating service conditions. The interaction between the arcing time and rate of rise of recovery voltage has been investigated enabling the short circuit performance of the interrupter to be segregated into three regions. Parameters improving the thermal and dielectric capability of the interrupter and consequently the short circuit performance have been identified, and in order to overcome the associated dielectric problems, several flush pipe configurations are tested and the optimum configuration ascertained. Successful performance of the rotating arc interrupter has been achieved at the 145kV, 31.5kA level.