Test site for nonstandard combined accelerated aging of medium voltage insulation systems

Presently, the wide usage of power electronics in electrical power systems brings a new type of voltage stresses of insulation systems. Power electronic systems, as high voltage dc systems, flexible ac transmission systems, voltage source convertors, static compensators etc., are usually using the pulse width modulation (PWM) that generates a wide spectrum of interferences. Harmonics and impulses with the main frequency content up to tens of kilohertz can arise as a consequence of mutual interaction between switching pulses emitted by power electronic component and distribution network passive parameters (resistance, inductance, and capacitance). Voltage distortions are superimposed to the power frequency voltage. Superimposed very fast and repetitive overvoltages can significantly decrease the life time of medium voltage devices. A novel test site for accelerated aging of medium voltage insulation system with new stress conditions was proposed and realized. The test site is able to simulate the voltage stress which more represents the real situation in power systems containing power electronics. Moreover, the proposed test site allows combining of the voltage stress with the thermal stress by high current flow in the cable conductor. The fundamental characteristics of test site components were determined and verified according to the preliminary proposal. The output voltage waveforms are discussed regarding to the real data gathered from measurements in distribution grid.