High Voltage Infrastructure Research Articles

Transmission line earthing system; Advanced design diagram for safety compliance

An electrical high-voltage power system is essential to support everyday electrical demands. Due to the increase in electrical loads, a more rigid design is required to ensure system compliance with standards and policies. High-voltage safety is the number one priority when it comes to the design, installation, commissioning, and operation of the electrical power system network. Safety compliance is getting more complex due to the joining infrastructure between residential and high-voltage projects. Nowadays, high-voltage infrastructure, including substations and transmission lines, is constructed near residential properties. This neighboring setup increased the safety concerns of high voltage systems, especially under fault or system malfunction situations. Safety concerns are addressed during the design stage and verified during the commissioning stages.The paper discusses the minimum transmission line earthing system requirements. This document provides a clear and consistent approach to assess transmission line earthing system design. The work contents comply with current IEEE standards including rigid author research outcomes. The works reduce the complexity of the assessment and explain the critical role of different sectors within the transmission line network. The work introduces the boundaries when the fault current analysis should include the earth grid resistance. A case study is also included.

Characterising ecological resource utilization by the endangered Egyptian vulture in Oman to better manage and mitigate electrocution risk

Electrocution is a threat to birds and can undermine their conservation status. We tracked 15 globally endangered Egyptian vultures (Neophron percnopterus) in Oman and used Resource Selection Functions (RSFs) to identify habitats important to vultures and locate places where electrocution risk is high. During daytime vultures selected rugged areas with low vegetative cover, and habitats near roads, waste disposal sites, and both high (>50 kV, large pylons) and medium voltage electricity infrastructure. At night vultures also selected rugged habitats with scarce vegetation. At night high voltage infrastructure was selected, especially in areas of relatively low ruggedness at higher elevations; medium voltage infrastructure was avoided at night. The pattern of infrastructure use suggested that vultures were using large pylons for night-time roosting, but used both large pylons and smaller poles for perching during the day. 54.2 % of 11–33 kV powerlines in the study area were within the top six habitat suitability categories, which also contained 87.3 % of 34,778 vulture daytime test locations. Retrofitting powerlines overlapping the highest suitability zones would have the largest immediate impact. Areas surrounding landfills were also important: 10.34 % of all test locations were located within 2 km of landfills, which contained only 14.5 km of 11–33 kV lines. Targeting these areas would provide high impact at low cost. These maps are particularly useful in Oman because it is a stronghold for resident endangered large birds (i.e., Egyptian vulture, lappet-faced vulture Torgos tracheliotos) and an important winter destination for endangered steppe eagles (Aquila nipalensis).

Reconfigurable Battery for Charging 48 V EVs in High-Voltage Infrastructure

48 V is emerging as a safe-to-touch alternative voltage level for electric vehicles (EVs). Using a low- instead of a high-voltage drive train reduces isolation efforts, eliminates the risk of electric shock, and thus increases the system safety. In contrast, fast charging of a 48 V battery would require very high currents and is incompatible with the widely established high-voltage electric vehicle charging infrastructure. Instead of employing additional on board power converters for fast charging, the concept of a reconfigurable battery is presented. A small-scale prototype system is designed consisting of eight 48 V lithium iron phosphate battery modules. In series configuration, they can be charged at 460 V with up to 25 A. In 48 V parallel configuration, the peak discharge current is up to 800 A. The MOSFET-based reconfiguration system also operates as a module charge balancer during high-voltage charging. The cost overhead for the reconfiguration system is estimated to 3% for a scaled-up full size EV. Due to the additional reconfiguration switch resistances, the simulation of a 48 V 75 kW electric vehicle in the World harmonized Light-duty vehicles Test Procedure showed a performance reduction of 0.24%.

Dynamic Frequency Support for Low Inertia Power Systems by Renewable Energy Hubs with Fast Active Power Regulation

This paper concerns the feasibility of Fast Active Power Regulation (FAPR) in renewable energy hubs. Selected state-of-the-art FAPR strategies are applied to various controllable devices within a hub, such as a solar photovoltaic (PV) farm and an electrolyzer acting as a responsive load. Among the selected strategies are droop-based FAPR, droop derivative-based FAPR, and virtual synchronous power (VSP)-based FAPR. The FAPR-supported hub is interconnected with a test transmission network, modeled and simulated in a real-time simulation electromagnetic transient (EMT) environment to study a futuristic operating condition of the high-voltage infrastructure covering the north of the Netherlands. The real-time EMT simulations show that the FAPR strategies (especially the VSP-based FAPR) can successfully help to significantly and promptly limit undesirable large instantaneous frequency deviations.

An autonomous drone-based system for inspection of electrical substations

In the years to come, large power grid operators will operate and maintain an ever-increasing asset base. New innovative solutions are needed to increase the quality and efficiency of asset management to avoid corresponding growth in resources and cost. To this end, autonomous unmanned aerial vehicles (UAVs) provide a range of possibilities. Here, we present a novel prototype solution for autonomous and remotely operated inspection missions with resident drones on electrical substations, comprising: (1) an autonomous drone with sense and avoid and robustness to harsh weather capability; (2) a drone hangar for remote operations; and (3) drone operations and data acquisition management software. Further, we discuss the possibilities and challenges that such a system offers and give an overview of requirements that are key to realizing the potential of drones for improved asset management. These requirements are based on years of operational experience with electrical substations combined with the lessons learned during the development and testing of our drone system. We also experimentally investigate safety distances between the drone and high-voltage infrastructure. We demonstrate the usefulness of our autonomous inspection solution through extensive field testing at one of Statnett’s fully operational electrical substations.

Technical feasibility of Japan-Taiwan-Philippines HVdc interconnector to the Asia Pacific Super Grid

High voltage direct current (HVdc) interconnector is an essential component for large-scale high voltage infrastructure expansion, duplication, and integration of existing power grids. High-voltage alternating current (HVac) grids are increasingly facing hybridization with HVdc, due to the augmented penetration of renewable power sources, and the technological maturation of Offshore Power Systems (OffPS). The authors investigate a submarine interconnector route, poorly explored by the literature, linking Japan, Taiwan, and the Philippines. This proposed offshore HVdc interconnector would support power trading between Japan, Taiwan, Philippines, Indonesia, and Australia. The proposal circumvents some contested territorial disputes in the East and South China Seas. The outcome of this research investigation is a Super-Grid topology that unveils some basic requirements of technical feasibility and reveals enhanced technical and environmentally-friend performance as compared to existing isolated national power grids of the affected countries. The proposed interconnector route lays down in seabed depth not exceeding 3 km. It aims at transmitting tens of gigawatts, clearing the path for a more sustainable and renewable-energy society in Japan, Taiwan, and the Philippines. This HVdc interconnector is still in the initial stage of feasibility studies, and it inspires further research on a possible and future Asia Pacific Super Grid.

Nanofluids in the Service of High Voltage Transformers: Breakdown Properties of Transformer Oils with Nanoparticles, a Review

The continuous development of electrical systems and high voltage transformers builds the need for looking for new insulating media or to improve the insulating properties of commercially available transformer oils (TO) by various modification techniques. One of these techniques is the modification of existing mineral oils by the addition of different types of nanoparticles in various concentrations. These types of materials, suspensions of nanoparticles called nanofluids, have found numerous applications in the energy industry, especially in heat exchanger systems and solar cells. Much research has been done on attempts to replace mineral oils (MO), which are harmful for the environment, with natural ester oils (NE), but to make this possible, it is necessary to improve the insulating properties of these oils, for example by adding nanoparticles. This paper presents an extensive overview of the insulating properties; including for AC, DC and the lightning impulse breakdown voltage; for both mineral and natural ester oils containing various type of nanoparticles (NP). It is presented that the use of nanofluids could improve the efficiency of existing high voltage infrastructures with a low financial cost.

Passive optomechanical electric field strength sensor with built-in vibration suppression

Methods for measuring low-frequency and static electric field strength are of great use in many areas ranging from meteorology to high-voltage infrastructure or safety. Nevertheless, all state-of-the-art methods have grave intrinsic drawbacks such as severe inherent field distortions or overpronounced temperature behavior. Recently, a method has been developed which allows for distortion-free and temperature-stable measurement. In this work, a micromechanical sensor based on this method is presented which features suspensions that suppress cross-sensitivities to vibrations. Two such types of suspensions were evaluated and compared in terms of their mechanical modes and susceptibility to electric fields and vibrations. It is shown that these suspensions indeed suppress the cross-sensitivities. The sensors exhibit field strength resolutions down to 737 V/m/Hz with a theoretical limit as low as 59.3 V/m/Hz.

A High-Efficiency Helical Core for Magnetic Field Energy Harvesting

Real-time data of high-voltage infrastructures collected by wireless sensors are the foundation of many smart grid applications. Energy harvesting can be an effective solution for autonomous, self-powered wireless sensors. In this paper, a coil with a novel helical core is proposed and optimized to scavenge the magnetic field energy efficiently near equipment carrying large currents. Due to the special design of the helical core, the path of the magnetic flux inside the core can be significantly increased, which leads to a reduction of the demagnetizing field. Therefore, the proposed core can generate a much higher flux density (hence more power) compared with conventional designs. The selection of the core material is studied and it is found that high permeability ferrite is the most suitable material. Experimental results show that the proposed helical coil with only 400 turns of wire can have a power density of ${\rm{2.1\,\mathrm{\mu} W/ cm}}^{3}$ when placed in a magnetic flux density of $7\,\mathrm{\mu} T_{{\rm{rms}}}$ . This value is bigger than any of the existing designs if placed in the same magnetic field. If more wires can be wound on the core, an even higher power density could be obtained. Therefore, the proposed design is a very efficient method for scavenging the magnetic field energy for a wide range of smart grid applications.

Network topology and resilience analysis of South Korean power grid

Abstract In this work, we present topological and resilience analyses of the South Korean power grid (KPG) with a broad voltage level. While topological analysis of KPG only with high-voltage infrastructure shows an exponential degree distribution, providing another empirical evidence of power grid topology, the inclusion of low voltage components generates a distribution with a larger variance and a smaller average degree. This result suggests that the topology of a power grid may converge to a highly skewed degree distribution if more low-voltage data is considered. Moreover, when compared to ER random and BA scale-free networks, the KPG has a lower efficiency and a higher clustering coefficient, implying that highly clustered structure does not necessarily guarantee a functional efficiency of a network. Error and attack tolerance analysis, evaluated with efficiency, indicate that the KPG is more vulnerable to random or degree-based attacks than betweenness-based intentional attack. Cascading failure analysis with recovery mechanism demonstrates that resilience of the network depends on both tolerance capacity and recovery initiation time. Also, when the two factors are fixed, the KPG is most vulnerable among the three networks. Based on our analysis, we propose that the topology of power grids should be designed so the loads are homogeneously distributed, or functional hubs and their neighbors have high tolerance capacity to enhance resilience.

Counterpoise Mutual Voltage and Its Impacts on the HV Transmission UGOH Pole Earth Potential Rise

Abstract High-voltage earthing system design is required to ensure safety compliance and adequate operation of the high-voltage infrastructures. The transmission lines form a solid part of the high-voltage infrastructure. The underground to overhead (UGOH) pole earth grid is one of the main challenges when it comes to transmission line earthing system design. To ensure safety compliance at low cost, counterpoise earthing is used at the UGOH pole for the underground lines. The counterpoise aids in lowering the UGOH pole earth grid resistance. This paper addresses the counterpoise analysis as currently being studied. Furthermore, it introduces the counterpoise mutual voltage between the faulted phase and the counterpoise and its impact at the UGOH pole earth potential rise. Case study is included.

Estimation of novel position for the current and potential probe for the fall of potential method

Earthing system is one of the main key elements in high-voltage safety management. It presents a safe working environment for workers and people passing by during a fault or malfunction of a power system. Commissioning the earth grid is a critical phase prior to the energizing of the high-voltage plant. Fall of potential method is commonly used to measure the earth grid resistance of the high-voltage infrastructure especially high-voltage transmission pole earth grid. The positions of the current and potential probe play a significant role that leads to precise results. This study endeavours to provide information in regards to the ‘Fall of Potential’ method. It includes the minimum separation required between the current probe and the tested grid. Furthermore, the novel location of the potential probe when the minimum separation between the current and electrode under test cannot be established is analysed. The case study results show the advanced accuracy in the tested result when deploying the novel method as provided in this study. The case study proves the advance accuracy of the proposed novel method especially when the testing area does not permit for a large separation between the tested grid and the current probe.

Grounding system impedance characterization using FEM

The exact knowledge of the grounding system impedance, including its expected variability, is a matter of paramount importance in the design of medium and high voltage infrastructures. The principles underlining the physical processes involved in grounding are well established and so are the engineering concepts regarding safe operation of the grounded systems. Quite a few theoretical expressions are widely used in the project stage of any installation. Unfortunately, these expressions are only valid for simple geometries and simplified material characteristics. Uncertainty arise from the intrinsic complexity of the grounding environment: buried grids and rods, reinforced concrete foundations surrounding them, weather dependent and non-uniform soil characteristics, etc To overcome these limitations, in this paper the finite element method is applied to obtain the grounding impedance and the potential distribution around a real grounding system excited with sinusoidal currents at several frequencies. Additionally, for validating purposes, a single vertical ground rod has been simulated and compared with the results obtained by other authors. FEM commercial software, in addition to some specific purpose user functions, has been used. The method presented in this paper can be applied to any real geometry, electrode configuration and type of soil.

Impact of electromagnetic radiation on cascaded failure in high voltage insulators

A cause of aging and cascaded failure of high voltage insulators is investigated by assessing the radiation propagating from a faulty insulator. The transfer of electromagnetic energy from corona discharge to healthy insulators situated on the same power pole is assessed. The results show that the high intensity of electric field associated with corona discharge on faulty insulators can lead to aging and finally failure of high voltage infrastructure.