For many decades, Geomagnetically Induced Current (GIC) has posed a significant risk over the electrical power grid infrastructures worldwide. The phenomenon occurs due to geomagnetic disturbance (GMD) and related space weather events arising from solar activity. It represents a potential hazard to the secure and safe operation of electrical power grids by causing half-cycle saturation of grounded High Voltage (HV) power transformers, relay misoperation, and increased reactive power demand in the power systems. Previous studies have shown that the occurrence of intense GIC is not limited to high and mid-latitude regions, but powerful space weather events can also result in intense GIC in power systems located in lower geographic latitudes. This study aims to estimate GIC and its impacts on a Malaysian power grid. A network model of the grid was constructed by using the Power System Simulator for Engineering (PSS/E). This represents the first attempt to study GICs in south-eastern Asian power grids since a region is considered to have low GIC risk up to now. During the analysis, firstly, we exposed the entire power network which includes 500 kV, 275 kV, and 132 kV system voltages to different geoelectric field strengths in the 0-180 • directions. The applied geoelectric fields were calculated based on benchmark value for 1 in 100 years of GMD events. Then we disconnected the 132 kV low voltage systems from the network model to investigate their influence on the calculated GICs. The results demonstrated that the most vulnerable substations to GMD events and experienced large GICs were those located in the middle of the Malaysian power network. The maximum GIC was recorded at substation 22 with the value of 44.58 A due to the peak electric field of 1.2 V/km at 100 • field direction. Also, the results showed that the calculated GICs slightly increased when 132 kV systems were removed from the power network, especially at the substations directly connected to these systems.INDEX TERMS Geomagnetically induced current, geomagnetic disturbances, space weather, energy, high voltage transformers, Malaysian power system.

Geomagnetically induced current (GIC) is a ground end manifestation of geomagnetic disturbances (GMDs) and space weather arising from solar activity, which causes half-cycle saturation and represents a potential hazard for a stable and safe operation of earthed high voltage (HV) power transformers. Previous studies have shown that the impact of GIC is not limited to high and mid-latitude regions, but it can also affect power systems located in lower geographic latitudes. This work presents the impact of GIC on HV transformers in the Malaysian power network. A detailed power network was modelled using the Power System Computer-Aided Design for Electromagnetic Transients including Direct Current (PSCAD/EMTDC) software. The entire network was subjected to a geoelectric field strength of 20 V/km at the northward and eastward directions. The GIC analysis has determined the most critical locations in the power network model that are prone to high GICs. The simulation results demonstrated that the most vulnerable substations to GMD events and experience the most severe GICs were those located in the middle of the Malaysian power network. The GIC effects and saturation levels of four transformers' types in these locations have been investigated over the transmission network. Under the GIC condition, transformers were driven into halfcycle saturation and their reactive power consumption drastically increased. Thus, conventional GIC mitigation systems based on neutral blocking devices (NBDs) were proposed and connected to the power transformers to block the GIC flow in their neutral paths. It was found that the GIC protection modes in the mitigation systems effectively eliminate the injected GICs in the neutral paths and are able to prevent the saturation occurrence of the transformers.

Geomagnetically induced current (GIC) has been a significant concern for the electrical power grid in high latitudes for decades. Its origin starts in the Sun; during extreme space weather, the magnetic field of the Earth varies rapidly. This variation induces electric fields at the Earth's surface and leads to GICs in manmade technologies. Power systems are the most affected by this induced current, which causes halfcycle saturation of power transformers and other issues. Understanding the behaviours and chain effects of this phenomenon is the key consideration in modelling the hazards to technological systems from space weather. In this paper, a comprehensive review of space weather, geomagnetic disturbances (GMDs) and GICs and their impacts on the power systems in both high and mid-low latitude regions is presented. Additionally, we highlight the most commonly used methods to model and calculate geoelectric fields at the Earth's surface and GIC in the power systems with respect to DC and AC analysis. In addition, we have classified the GIC effects on the different power system components. Moreover, the possible solutions and mitigation techniques to eliminate or reduce these effects based on different GIC blocking devices are reviewed in this work. This work provides researchers and power system operators a shortcut road path to understanding GIC phenomena, modelling and calculations, effects, and mitigation of these effects.

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This paper investigates micromachined antenna performance operating at 5 GHz for radio frequency (RF) energy harvesting applications by comparing different substrate materials and fabrication modes. The research aims to discover appropriate antenna designs that can be integrated with the rectifier circuit and fabricated in a CMOS (Complementary Metal-Oxide Semiconductor)-compatible process approach. Therefore, the investigation involves the comparison of three different micromachined antenna substrate materials, including micromachined Si surface, micromachined Si bulk with air gaps, and micromachined glass-surface antenna, as well as conventional RT/Duroid-5880 (Rogers Corp., Chandler, AZ, USA)-based antenna as the reference. The characteristics of the antennas have been analysed using CST-MWS (CST MICROWAVE STUDIO®—High Frequency EM Simulation Tool). The results show that the Si-surface micromachined antenna does not meet the parameter requirement for RF antenna specification. However, by creating an air gap on the Si substrate using a micro-electromechanical system (MEMS) process, the antenna performance could be improved. On the other hand, the glass-based antenna presents a good S11 parameter, wide bandwidth, VSWR (Voltage Standing Wave Ratio) ≤ 2, omnidirectional radiation pattern and acceptable maximum gain of >5 dB. The measurement results on the fabricated glass-based antenna show good agreement with the simulation results. The study on the alternative antenna substrates and structures is especially useful for the development of integrated patch antennas for RF energy harvesting systems.

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Geomagnetic disturbance (GMD) arises during space weather and solar activity can result in geomagnetically induced current (GIC) flow in the grounded power transformers in the power network. This GIC may cause half-cycle saturation of transformers and lead to severe damage or blackout. To block the GIC flow into the power transformers, the neutral blocking devices (NBDs) based on capacitor banks are often installed in the neutral ground paths of transformers to mitigate the GIC. However, the high voltage (HV) can build up across these capacitors during ground faults and may cause a ferroresonance phenomenon in the power network. This phenomenon generates high voltages/currents in the transformer windings and results in transformer failure. This work investigates the effect of connected NBDs to the power transformers on the potential power network ferroresonance in Peninsular Malaysia. The complete analysis was carried out using the Power System Computer-Aided Design for Electromagnetic Transients including Direct Current (PSCAD/EMTDC) software. These transformers were selected in the power network due to the sensitivity of their locations to GMD events. The NBD systems were tested under different working conditions. The simulation results found that the metal oxide varistors (MOVs) arresters in NBDs fault protection mode effectively clamped ferroresonance overvoltages below the protection level under faulty conditions. Also, the results showed that GIC protection modes with 1 Ω and 3180 μF in the mitigation systems had the lowest ferroresonance overvoltages in the neutrals of the transformers under faulty conditions. Based on the results, the recommendations were provided to the local power utility which will help to improve the reliability of the power supply to the consumers.

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