Development of inductive coil sensor based on Rogowski coil for arcing fault in medium voltage (MV) measurement

Arcing fault overvoltage is one of the most common problem that always occur in both low voltage (LV) and medium voltage (MV) systems. The arc fault overvoltage in high voltage system is the most dangerous which can easily cause explosion of electrical components such as cable, transformers, switchgears and other equipment. The cause of arc fault overvoltage is due to the loosen cable termination at bus bar and transformers terminal, cable jointing and others. In order to reduce the arc fault risk, the arc circuit interrupter (AFSI) technology and arc fault detectors (AFD) have been developed. However, these devices are more suited for LV or domestic application. For applications in medium voltage (MV), a new arc fault sensor is needed to overcome this problem. Frequent arcing fault overvoltage can cause an interruption of the electrical system which may breakdown the system. Thus, to overcome this matter, the arcing fault sensor was developed in this research. The Rogowski coil (RC) which is one of the inductive coil group was selected as the arc fault detection sensor. Finite Element Method (FEM) was used for electromagnetic flux density, B analysis on RC geometrical and number of turns effect by modelling three different types of RC which are the rectangular, oval and circular cross-section. Based on FEM simulation results, the rectangular cross-section of RC had the highest electromagnetic flux density among the circular and oval cross-section. The mutual inductance calculation of rectangular cross-section has also been performed and compared to the FEM simulation results. There were seven (7) rectangular cross-section RC sensor prototypes that were fabricated using three-dimensional (3D) printer with various number of turns ranging from 20 to 100 with the cross-sectional area ranging between 200 mm2 and 1050 mm2. The acrylonitrile butadiene styrene (ABS) material was selected as the RC sensor core because it has low conductivity, categorized as an insulator, adequate rigidity, good thermal stability, exhibit high toughness even in cold conditions, chemical resistance, environment stress cracking and excellent mechanical properties. The sensor performance verification in terms of sensitivity and bandwidth was conducted with an experimental measurement that was done in the high voltage lab. Based on the experimental results, the RC sensor prototype RC2A5 (fabricated in this research) which has the highest number of turns (100 turns) produced excellent sensitivity at 0.56 kV/mA. However, the bandwidth of RC2A5 descended to 3.51 MHz which is the lowest bandwidth. Whereas, by reducing the number of turns to 20, the RC sensor prototype RC2A1(fabricated in this research) ascended to 7.93 MHz which is the highest bandwidth, but its sensitivity drops rapidly to 0.30 kV / mA. From the obtained results, it can be concluded that that the lower number of turns produced better bandwidth for the RC sensor but reduces the sensor sensitivity significantly. The best RC sensor developed in this work was proposed to be used as an arc fault overvoltage measuring sensor for the future.