No abstract

Recently, addition of nanofillers to insulating fluids to increase its breakdown voltage finds a great interest from researchers. Understanding the reasons of the increased breakdown voltage with addition of nanofillers at certain loadings to insulating fluids is of great importance. Hence, understanding how electric breakdown occurs in nanofluids can help researchers to select the more suitable nanofiller material, nanofiller particle size ....... etc. to be added to insulating fluids. Therefore, in this paper, a generalized electric breakdown mechanism of insulating nanofluids is presented. The generalized mechanism takes different parameters into consideration. These parameters are nanoparticle permittivity, nanoparticle size and insulating fluid temperature. To demonstrate the validity of the generalized breakdown mechanism, theoretical computations are carried out using finite element analysis. Also, breakdown experiments considering transformer oil are carried out considering different nanofiller materials, nanofiller sizes at different temperatures.

The measurement of a power frequency current including low- and high-order harmonics is of great importance in calibration as well as in testing processes. Therefore, this paper presents the measurement of the power frequency current of light-emitting diode (LED) luminaires. LED luminaires were chosen as their input current includes both low- and high-order harmonics. The measurement process depends on reconstructing an LED luminaire current without using the coil parameters. Hence, the current reconstruction process is designed to be dependent on the measured characteristics of the Rogowski coil itself considering the frequency range at which the measurement process is required. An evaluation of the proposed measurement process was theoretically and experimentally carried out. A theoretical evaluation was carried out using MATALB SIMULINK software. However, the experimental evaluation was performed by building a Rogowski coil to measure the input currents of different LED luminaires having different power ratings of 300 W, 400 W, and 600 W. The currents measured using the Rogowski coil were compared with reference currents measured using a standard measurement technique. The obtained results show the efficacy of the proposed measurement method.