The Estimation of the Geomagnetically Induced Current Based on Simulation and Measurement at the Power Network: A Bibliometric Analysis of 42 Years (1979-2021)

GIC (geomagnetic induced current) is a natural current that flows through a conductive substance. The purpose of this study is to provide bibliometric analysis on the computation of the GIC at the Power Network, since determining the backflow current’s threshold limit is crucial to avoid electrical equipment failure. The methodology of the study includes topics, scope, and eligibility, as well as screening and an analytical screen paper. From 1979 to 2021, we investigate the evolution of bibliometric studies on the assessment of the GIC at the power network. According to the statistics, there are 601 Scopus articles and 357 Web of Science (WoS) papers in the study on GIC at the power network that focus on estimation from 1979 to 2021. According to the data, the Engineering and Energy disciplines contribute the most to research on predicting the GIC at the Power Network. The words “geomagnetically induced current,“ “reactive power,“ and “geomagnetism“ are commonly used instead of “magnetic storm,“ “power grids,“ and “geoelectric fields.“ The bibliometric method encompasses themes, scope and eligibility, screening, and screen paper for all publications in a search for developing subjects based on Scopus and WoS to map the time-trend, disciplinary distribution, and high-frequency keywords.


I. INTRODUCTION
The interaction between the solar wind and the earth magnetosphere induces a time-varying geomagnetic field on the ground, which flows through ground-based systems such as power grids, pipelines, and railways via the connecting conductive material [1]- [4]. Geomagnetically Induced Current is the current that travels through the conductive substance (GIC). Transformer half-cycle saturation, harmonic distortion, and reactive power loss are all caused by GIC flows in the power network [5]- [9]. GICs have previously caused transformer melting [9] and, in some cases, major power outages, such as the historic breakdown of the Hydro-Québec power system in Canada during the geomagnetic storm of March 13 [2], [10], [11], which left the 6 million citizens of Québec without power for more than 9 hours. In today's world, the cost of a widespread power outage is expected to be in the billions of euros per day for advanced economies [2]. From 1979 to 2021, a huge number of studies on GICs in high-voltage (HV) Power Networks were published Initially, studies on GIC found that the impact of GIC is more dangerous in the polar zone than in the high-latitude region. The GIC study has attracted international attention because of an unknown threshold limit that could pose a threat to the HV power network. The computation of the geoelectric field from magnetic field fluctuation data in combination with an electrical conductivity model of the region [2], [12]- [16] is a key component for estimating the GICs level (1). (2) a correct description of the HV transmission system, including network resistances, substation earthing points, and power line paths [2], [17]- [19]. The number of research papers being published is steadily rising. Only a handful of the research topics include concepts, methodologies, applications, and management. As a result, providing a summary of published research is advantageous so that interested researchers can rapidly learn about the study profile thus far. By applying the special search keyword, the bibliometric study was able to examine the academic research output connected to "The Estimation of Geomagnetic Induced Current based on Simulation and Measurement at the Power Network." Scopus' publication index was used to acquire the entire examined publication. The data was collected between 15 July 1979 and 10 November 2021 at 09:15:00 Malaysian Time on 10 November 2021. The search categories are the publication's Title and Abstract keywords, and the results are then given.

II. LITERATURE REVIEW
There are about 601 publications in Scopus and 357 publications in WoS consist of the related study on "The Estimation of Geomagnetic Induced Current based on Simulation and Measurement at the Power Network". The earliest papers on GIC are in 1979 studied the Harmonics and Switching Transient in the presence of Geomagnetic Induced Current publish on 2 February 1981. The GIC recorded from the neutral cable of the three-phase transformer cause halfcycle saturation [20]- [25]. Due to the use of extra-high voltage (EHV) and ultra-high voltage (UHV) lines for electrical transmission, the observed GIC from the neutral point of the transformer surpasses 100 amps. The issue of GIC has become more acute because of the more strongly anchored practice of EHV and UHV [20]. There are various studies on GIC in the 1980s that are related to the high voltage power grids [26]- [34]. The GIC papers in 1980s focus on the GIC effects on the harmonics, switching transient, transformer and relay performance, high voltage direct current (HVDC) converter and transmission system [26]- [34]. In the 1990s the Study on GIC evolved to the simulation on the GIC by using a computer program [35], the design of the blocking/bypass device to prevent the flow of the GIC in Power System [36], neural network application on GIC [37], and Systematic Finite Element Simulation (FEM) on GIC [38].
The study on GIC evolved over time, therefore identifying the cluster of the GIC in the year 2021 is important to understand the current trend of the study on the GIC. From 2000 to 2010, the study on GIC evolve to the calculation of the surface of an electric and magnetic field of geomagnetically induced current from the ground [39], study on the ionospheric current that causes rapid geomagnetic variation which results in strong GIC [40], improved model of the GIC simulation and introduction to the test model for GIC computation algorithm [41]. The study on the GIC in low latitude transmission networks from Brazil is also being investigated majorly based on the geomagnetic disturbance (GMD) data on 7th to 10 th November 2004 [42]. China identifies high GIC from the Power Network based on the study by [43]. There are also study conducted for the Sweden 400kV power grid to analyze the GIC level [44]. From 2010 to 2021, the study on GIC estimation evolved and about 427 publications on the GIC at the Power Network have been traced by using the special keyword.
The investigation of GIC was conducted at both mid and low latitude to determine the GIC's threshold limit. The GIC research from 2010 to 2021 has made significant contributions to the area of study, including assessing the finite element approach for modelling geoelectric fields [45], and evaluating the finite element method for modelling geoelectric fields [46], modelling a 3D earth conductivity structure for GIC computation [47], and investigating severe auroral electrojet indices that result in high GIC [48], Geomagnetic Induced Currents in Power Transformers: Core Saturation Effects [49], Suppressing GIC with Control Ground Resistance on the Transformer [50]. Statistical Relationship between the variation of the Geomagnetic field, Reactive Power Optimization Strategy for Mitigating Voltage Fluctuation in Power Network Caused by Geomagnetic Storm [51], Latitudinal Dependence of Geomagnetically Induced Current during Geomagnetic Storm [52], Reactive Power Optimization Strategy for Mitigating Voltage Fluctuation in Power Network Caused by Geomagnetic Storm [53], predict violent GIC threatening Power Grids using PC indices [54], and Study the Spatial Scale of the Geomagnetic Pc5/Pi3 pulsations as a factor of their efficiency in the generation of Geomagnetically Induced Current [55]. The major contribution of this paper is highlighted as follows: 1) The bibliometric study of "The Estimation of Geomagnetically Induced Current at the Power Network" is examined to better understand the field's recent development and key structure. It will serve as a starting point for scholars interested in working on this under-researched but potentially important topic. 2) Based on the Scopus and WoS indices, the bibliometric analysis examines the growth of research in terms of the number of publications and total citations obtained over time. 3) In addition, the best of 20 entities in the field of "Geomagnetically induced current at the power network" are extracted in terms of authors (productive and influential), discipline, source (productive and influential), countries, institutions (productive and influential), and highly influential papers. 4) The latest and influential works are summarized and explained in depth based on the bibliometric analysis, with a focus on "estimation," "geomagnetically induced current," "power grid," and "power network." 5) The researchers can infer the inner structure and acquire a broad image of the area based on this research 6) This is a one-of-a-kind study that emphasizes both the bibliometric and detailed review of the Geomagnetically Induced Current in the study.

III. DATA COLLECTION AND METHOD
The data is gathered from the Scopus and Web of Science repositories, which are the two most popular bibliometric databases. Our primary goal is to do a bibliometric analysis of "GIC," hence the keywords included in the search query are as follows: Title-Abstract-Keyword: (''analyze*'' OR "analyse*" OR "identify*" OR "estimate*" OR "estimation*" OR "calculation*" OR "calculate*" OR "evaluate*" OR "evaluation*" OR "predict*" OR "prediction*" OR "measure*" OR "measurement*" OR "simulation*" OR "simulate*" AND "geomagnetic* induced current*") AND Title-Abstract-Keyword: ("power grid*" OR "power network*" OR "transmission line*" OR "transformer*" OR "network*" OR "grid*") Timespan: 1979-2021. The total publication found by searching the following keywords, according to Scopus, is 601. From the 15th to 20th of July 1979, the earliest article based on the search query was titled "Harmonics and Switching Transients in the Presence of Geomagnetically-Induced Currents" authored by [20].
The number of publications indexed by WoS is 357, with the earliest one dating from May 1992 and named "Geomagnetic Effects Modelling for the PJM Interconnection System .2. Geomagnetically Induced Magnetization as Current Study Results" authored by [56]. Author, title, abstract, country, citation record, and author affiliation are among the tags that are retrieved (from WoS and Scopus). In WoS, a total of 357 publications were extracted, with articles (263), reviews (2), conference papers (105), book chapters (2), and notes (2)    number of received citations count divided by the total number of publications. The Impact Factor (IF) is a commonly used metric for evaluating journals. It is derived using the average citations of that journal's publications over the previous two or five years. Fig. 1 shows the flow diagram of the search strategy for bibliometric analysis and Fig. 2 shows the keyword included in the search group of Scopus and WoS before being analyse by VOS viewer, Publish and Perish software and readymade bibliometric analysis template.

IV. BIBLIOMETRIC ANALYSIS
This section is divided into sub-sections such as research growth and most productive authors, topmost subject areas, top source referenced, country-by-country analysis, institution-by-institution analysis, and highly influential papers in the field of "estimate geomagnetically induced current".

A. RESEARCH GROWTH AND PRODUCTIVE AUTHOR
The field of "Estimation of Geomagnetically Induced Current in Power Network" has gained a reputation in recent years due to its huge significance in various fields.
The potential of the study on the Estimation of the GIC at the Power Network is increasing and the major growth started in 2013 and still increasing until the year 2020. In the year 2021, the projection of the whole publication is still not yet known since the acceptance of the publication is still open. Fig. 3   There is another subject area that contributes to the research study. Since the research topic is a very vast field, the study on the research field fills the gaps in many subject areas which contribute to publication in various fields. In the academic circle, the journal publication is used to enhance the progress in the related subject area. The new publication will be updated continuously to enhance the knowledge in the field. We have shortlisted the top 20 Journals that are publishing works on "Estimation of the GIC at the Power Network" as shown in Table IV  Africa's Sustainable Energy for AD Agenda (AFRICON) with (TC = 0) and ranked 20 th . In terms of percentage, All the Journal Sources contributed to the publication evenly. The highest percentage was both filled by Space Weather Journal with Scopus (13.81%) and WoS (21.289%).

C. COUNTRY WISE AND INSTITUTION WISE
We have extracted results based on work distribution over several countries. The related work on "The Estimation of Geomagnetic Induced Current based on Simulation and Measurement at the Power Network" by several countries is shown in Fig. 4 Table V, the only Asian country in the list is China which is located between Mid and Low latitude region, and South Africa is the country from Africa which is also located between Mid and Low latitude region. The rest of the country are from

D. TOP 20 HIGHLY INFLUENCE PAPER
The Top 20 Highly influential papers based on the Subject Area are ranked based on the Citation number of the paper. The paper which highly cited based on Scopus and WoS is   Table VI and VII listed the Top 20 influential paper in Publication in Scopus and WoS.

E. BIBLIOGRAPHIC LANDSCAPE
In this section, we visualize the bibliographic connection cluster between the top authors in the research field and the field of the study which the authors involved. The simulation is conducted by using VOS viewer which is a platform used to simulate the literature study [57]. It's a tool for visualizing a network of publications, authors, institutions, subject areas, and countries, among other things. The number of times two entities (either writers or countries) cite the same entity is known as bibliographic coupling. It specifies the node-to-node disciplinary connections. Fig. 5 and Fig. 6 visualize the bibliometric cluster according to WoS and Scopus. There are nodes (shown as authors) and links between the nodes in the diagrams. The overlap between the common references in the papers as indexed by the respective repository is  represented by the breadth of these links. In Network Visualization (NW) modes, Nodes are also distinguished by their color.
A cluster of comparable elements is formed by nodes of the same color. A cluster is a collection of elements that form a logical unit. The more authors in a cluster, the more co-cited work and linked study topic there is. In Overlay Visualization (OV) mode, the colors indicate the duration of the publication in the Network. The deep blue indicates the papers is the earliest publication on the subject area and bright yellow indicates the new publication in the field. The 2 nd biggest cluster is from the dark green cluster with

V. DISCUSSION OF THE RESEARCH WORK ON THE SUBJECT AREA
In this section, we utilized VOS viewer to visualize the most common keywords and analyze what authors hoped to achieve in the most significant articles on the topic of "The Estimation of the GIC based on Simulation and Measurement in Power Network." This section also provides the reader with the rationale that has been used to address big data challenges in recent times, as well as potential areas to research in the future, thereby providing a clearer and better perspective for future studies.

A. KEYWORD SUMMARY ON GEOMAGNETIC INDUCED CURRENT AND GEOMAGNETIC DISTURBANCE
The effect of the Geomagnetic Disturbance on the formation of the GIC is due to the solar storm or a highaltitude nuclear detonation [58]. There are numbers of research conducted to mitigate the level of the GIC throughout the world. In power grid, the level of the GIC is important in evaluating the effects of geomagnetic storm [59]. The earliest study related to geomagnetic disturbance believe that its only threaten the technological system that are elongated in latitudinal (W-E) direction [1], [60]. Some studies show that the impact from geomagnetic disturbance existed considerably lower in variability to its derivative elongated meridionally [60]. The impact from geomagnetic disturbance to the formation of the GIC is higher in high latitude region due to the more prominent geomagnetic activity [61]- [65]. The impact of geomagnetic activity on GIC in the medium and low latitudes was still present, but not as severe as in the high latitudes.  [61] conducted the study on the 3D lateral conductivity map with surrounding ocean to model the geoelectric ground response due to the magnetic field. This process provides higher accuracy on the estimation of the GIC instead of the 1D lateral conductivity map. Klauber et al., 2020 [8] published a paper on the importance of GIC estimation during magnetic disturbances, stating that GIC estimation during magnetic disturbances is a critical aspect of realtime monitoring and management for power grid operations and control. Situational awareness is provided during GMD incidents because to increased interest in the consequences of GIC and effective mitigation techniques. According to Papers by S. M. Zhang & Liu, 2020[67], geomagnetic storm disasters have a substantial impact on the electrical system's safe and stable functioning.
Serious geomagnetic storm disasters can result in a chain reaction of power system failures, including voltage breakdown. As a result, it's critical to assess and assess the operating risks of power systems during magnetic storms. Based on the paper by Wang et al., 2020[68], the author approach the study by applying the machine learning to detect the GIC in the power grids. The author examining the measured currents from the current transformer (CTs) to detect GIC by using hybrid time-frequency analysis combined with machine learning technology. Based on the paper by Haddadi et al., 2020[69], the author studied the test case for geomagnetic disturbances and establish the validation work based on the software simulation to establish the model for GMD benchmark.
Based on the review journal paper on the GIC from [70] the important aspect in modelling the threats to technological systems from space weather is understanding the behavior and chain consequences of this event. This study provides a detailed overview of space weather, geomagnetic disturbances (GMDs), and geomagnetic interference (GICs), as well as their effects on power systems in both high and mid-low latitude locations. The research study conducted by Shu-Ming Zhang & Liu, 2020 [71] developed GIC benchmark model to calculate GIC from East-China 1000kV ultra-high voltage (UHV) and 500kV extra-high voltage (EHV) power grids under a uniform geoelectric-filed of 1V/km. The study found that the characteristics and pattern of the GIC in UHV power grid and identify the high-risk nodes which can be vulnerable to GIC encroachment. The first GIC measurement for 400kV Mexican Power Grid was made in a paper by Caraballo et al., 2020 [72] The study discovered that in the event of a Carrington-like event, GIC ranging from 25 to 150 Amp might impact the power system under a homogenous 1V/km east-west geoelectric field.
According to a study by Švanda et al., 2020 [73] on the immediate and delayed response of the electrical power grid to geomagnetic storms, there is a 5-10 percent increase in the recorded anomalies in the Czech power grid in the 5day period following the start of geomagnetic activity, and this fraction of anomalies is most likely related to GIC exposure. The author did a measurement and simulation on the GIC based on the Chinese low-latitude substation during geomagnetic storms based on a study by J. J. Zhang et al., 2020 [3], The results show that the physical-based model is better suitable to the prediction of GICs at lowlatitude power networks during storms than the persistence model. Study by Shuming Zhang et al., 2020 [74] on the Kalman filter approach on the model and method of calculating and analyzing GIC disturbance using reactive power measured by wide area measurement systems (WAMS) shows that reactive power measured by phasor measurement units (PMUs) can be effectively used to calculate and analyze GIC-Q in transformers, which is important to prevent power grid disasters caused by magnetic storms through dispatch and operation. The study by Nazir et al., 2021[58] examines the state of the art in GIC mitigation and elimination strategies, as well as their limitations, and introduces converter-based strategies as a new avenue of power system protection against GICs by presenting novel strategies that involve integrating the proposed schemes between the neutral and ground of power transformers. According to a study conducted by Behdani et al., 2021[75] on the investigation of the power transformer ferro resonance phenomenon caused by GICs in series capacitor compensated networks, GICs can significantly increase the vulnerability of power transformers to the occurrence of ferro resonance phenomena. According to a study by P. Yang et al., 2021 [76] on static voltage stability during geomagnetic storms, using a 1V/km generated geoelectric field significantly reduces static voltage stability, posing a serious threat to the power system.

B. KEYWORD SUMMARY ON REACTIVE POWER
When Reactive power is the situation where the power that flow back from a destination toward the grid in an alternating current scenario. Study conducted by Piccinelli and Krausmann, 2018 [77] that analyzed the behavioral of the Power System operational mode during geomagnetic storm found that the geomagnetic storm change the topology of the system, varying path of geomagnetically induced currents and inducing a local imbalance in the voltage stability superimposed on the grid operational flow. Transformer saturation will increase reactive power and cause imbalance and voltage instability for the entire system. Few episodes of instability were found in correspondence with existing voltage instability due to the underlying system load. Based on the study conducted by Halbedl et al., 2018[10] on the noise problem in some transformers in Austria. The study found that high geomagnetic disturbance led to high currents according to the simulation and confirm by the measurement data. This current can drive transformers or instrument transformers into half-cycle saturation which lead to higher no-load current, and the reactive power consumption raise.
According to a study conducted by Joo et al., 2018 [78] on the influence of geomagnetic disturbances on Korean electric power systems, their system maintains voltage stability and increases reactive power throughout the impact of the geomagnetic storm. The Korean electric power system meets all applicable US standards and ensures system stability. According to a study conducted by Stork & Mayer, 2019 [79] on geomagnetism, magnetic storms, and methods of estimating geomagnetic induced currents on power transformers, the transformer's reactive power increases when it is running in semi saturation mode. The increase in Joule losses in the winding, the iron of the transformers, and the transformer tank occurs when higher harmonics become more prevalent. High-altitude electromagnetic pulses (HEMPs) are bursts of electromagnetic radiation in transmission lines, according to a study done by Jeong, 2019 [80] The geomagneticallyinduced currents and increase in the reactive power absorption of the transformer in the power system were calculated using the Direct Current (DC) equivalent model of Korean power systems. The impacts of detonations at five target locations were compared in the study. It was determined that when affected by an E3 HEMP, Korean electric power systems are unable to maintain their stability.
The study conducted by Zawawi et al., 2020 [7] on the impact of GIC on selected 275kV sub power system network in Malaysia find out that the value of 315.10 Ω neutral earthing resistor can be used to limit the GIC current flow and thus provide protection to the power system network. Bejmert et al., 2020 [81] conducted a study on GIC on difficulties originating from DC excitation of power transformers due to geomagnetically induced currents (GIC). This study tallied the number of times the transformer differential protection tripped and proposed two GIC detection algorithms capable of providing adequate transformer differential protection blocking. Based on Zawawi et al., 2021 [82] work on GIC modelling on the impacts of a GIC on a three-phase power transformer that includes half cycle saturation and reactive power consumption. The magnitude flux and magnetizing current of the power transformer, as well as reactive power consumption, rise because of the simulation results under GIC conditions, potentially leading to power system instability.

C. KEYWORD SUMMARY ON POWER TRANSFORMER AND HARMONIC ANALYSIS
The formation of the GIC usually associated with power transformer due to connectivity existed between the earth surface and the neutral cable of the transformer. Based on the study conducted by Behdani et al., 2021[75] on the investigation of the power transformer ferro resonance phenomenon caused by GICs in series capacitor compensated networks, GICs can significantly increase the vulnerability of power transformers to the occurrence of ferro resonance phenomena. Ferro resonant waveforms, which are extremely distorted and heavily laden with harmonic content, can result in poor power quality and possibly protection system failure. Odd and even harmonics are present in significant levels and interact with fundamental-frequency voltage and current components, according to a study by Haddadi et al., 2021[83] on test case for geomagnetic disturbances and establish the validation work based on software simulation to establish the model for GMD benchmark.
According to a study by Nazir et al., 2021 [58], an AC offset that drives power transformers into saturation can result in a substantial draw of reactive power, increased noise level, damage to shunt capacitors and harmonic filters, and improper operation of power system protective equipment. From Heyns et al., 2021 [84] states that recently risk analysis has been formalized with North American Electric Reliability Corporation (NERC), in compliance with Federal Energy Regulatory Commission (FERC) regarding geomagnetic disturbance reliability standard that associated with GIC risk which cause damage to transformers, with a lesser emphasis on control system disruptions and harmonic production. GIC may generate increased noise emissions, thermal heating spots in transformer's iron due to eddy currents, more harmonic emissions, and voltage disturbances, according to a study by Halbedl et al., 2018[10] on the noise problem in some transformers in Austria. As these DC currents (quasi-dc currents for GIC) flow through transformer windings, a series of reactions such as increased harmonic, temperature of oil, vibration, and noise would occur connected with the half cycle saturation of the transformer core, according to a study by H. Lu et al., 2018[85]. The DC flowing in the transformer wind can bias the transformer core and produce half-cycle saturation, causing the magnetizing current to distort significantly, resulting in a sudden increase in the harmonics of the magnetizing current. Electrical measurements of voltages, currents, harmonics, and reactive power, as well as the search coil outputs, were recorded in a study by Chisepo et al., 2018[86] on part cycle, half wave saturation of a power transformers core produced by leaky DC or Geomagnetically Induced Current. The flux distribution in and around the core was determined using the search coil measurements.
According to a study on GIC and harmonic distortion in single phase bank transformers in substations by Clilverd et al., 2018[87], very low frequency (VLF) wideband measuring equipment detects the presence of power system harmonics and high-voltage harmonic distortion. Within 25 hours, two solar wind shocks occurred, resulting in four different GIC episodes. Two GIC events were linked to the occurrence of the shocks itself. There was no visible harmonic production because of these significant but shortlived GIC impacts. The third (150 Hz) harmonic is prominent in the neutral current of the power network, according to a study by Zirka et al., 2018[88] on the capabilities of a topological model of a three-phase, fivelimb transformer to accurately describe its response when subjected to geomagnetically induced currents. Because the current returning to the distant generator in the back-toback configuration is equal to the total of currents in the neutrals of the two transformers, this is the case. Harmonic currents may cause relay mis operation and accidental disconnection of reactive power sources such as static VAR compensators, according to a study by Kazerooni & Overbye, 2018[89] on line switching as a remedial action to safeguard transformers from geomagnetic disturbances (GMDs).
According to a study conducted by M. Yang et al., 2020 [90] on the physical performance of half-cycle saturation and technical solutions to inrush like half-cycle saturated currents, the resulting half-cycle saturated inrushlike current poses significant threats to the safety and economic operation of the entire ac power system, including transformer vibrations, audible noise, hotspot in transformer, excessive reactive power loss, harmonics, and increased thermal and mechanical loads. Study by Wang et al., 2020[68] on using machine learning to detect GIC in power grids, the harmonic components generated by GICs act in a variety of ways, and present detection systems do not take into account such complicated interference.
Based on the study by Haddadi et al., 2020[69] on the test case for geomagnetic disturbances and the validation work based on software simulation to establish the model for GMD benchmark, large GICs can cause prolonged unidirectional saturation of transformers, which generates harmonics and increases transformer var consumption. Protective relays may unintentionally trip needed equipment due to harmonic currents. Based on the study by Abda et al., 2020[70], the exposure to voltage unbalances and harmonics caused by half-cycle saturation in the primary circuit if there is GIC presence in the secondary wye circuit is caused by half-cycle saturation in the primary circuit if there is GIC presence in the secondary wye circuit. In the rotor's end rings, positive sequence harmonics may create mechanical vibrations, and even the harmonics themselves may generate excessive heating [6], [50], [91]- [95]. Generator protection relays, such as traditional negative-sequence relays, are designed to respond to a fundamental frequency imbalance. They may work incorrectly or not at all in reaction to harmonic currents during GIC events.
According to a study by S. M. Zhang & Liu, 2020[67] on the significant impact of geomagnetic storms on the safety and stable operation of power systems, the analysis method of harmonics caused by excitation saturation related to GIC level, transformer type, parameters, and other factors is similar to that of DC bias caused by DC grounding the electrode current, which is limited in space and will not be described in detail. According to a study by Li et al., 2020[96] that proposes a new reduced-scale model (RSM) equivalent circuit to reflect the actual operation of the UHV transformer under DC bias, the distortion of excitation current rises sharply as the DC bias current increases, with the first half cycle being the most affected. The even harmonics are caused by the DC bias current; the second harmonic virtually grows linearly with the DC bias current, whereas the growth rate of the high harmonics drops as the DC bias depth increases.

D. KEYWORD SUMMARY ON TRANSMISSION LINE
The harmonics components generated by GICs act in a variety of ways, and current detection systems do not take into account such complicated interference states that the effect of a geomagnetically-induced electric field on a power grid is taken to be equivalent to a set of voltage sources imposed on its transmission lines between various grounded points C. Liu, Wang, et al., 2018[97]. The integral of the geoelectric field along the line equals the magnitude of the voltage, converting the GIC computation into a circuit issue. The analysis suggests that the North European power transmission system is fairly resistant against extreme space weather events, according to a study by Piccinelli & Krausmann, 2018[77] that looked at the behavior of the Power System operational mode during geomagnetic storms. Only a few incidents of instability were detected in conjunction with an existing voltage instability due to the underlying system load when considering transformers more prone to geomagnetic storms.
According to a study conducted by Roberta Tozzi et al., 2018 [52] on how GIC amplitude varies with latitude during six major geomagnetic storms that occurred between 1989 and 2004, geomagnetically induced currents (GIC) can flow through infrastructure networks such as railroads, power transmission lines, and pipelines, causing damages ranging from slow degradation to immediate ruptures and malfunctioning. According to a study by Joo et al., 2018[78] on the influence of geomagnetic disturbances on Korean electric power systems, the Korean electric power system meets the relevant standards in the United States and maintains system stability during a major geomagnetic disturbance. GIC neutral currents in transformers are calculated using the NERC's benchmark event, DC voltages, and GIC currents on transmission lines. The maximum GIC neutral is projected to be 51.13 A when Korean power systems are exposed to a 1.2 V/km geoelectric field, which meets the NERC requirement of 75 A as the maximum permissible current. The disparities between measurement and simulation can be detected in the zone of "rapid" fluctuation within seconds, according to a study by Halbedl et al., 2018[10] that worked on actual results about geomagnetically induced currents (GIC) in the Austrian transmission system. Currents from underground railways that operate on DC flow through the transmission grid, according to a careful examination of the periods of occurrence. Constant expansion of energy networks, the growth of their interconnections, increased load, and conversion to low-resistive transmission lines, according to Belakhovsky et al., 2018[60] study on the analysis of geomagnetically induced currents based on new characteristics to describe the variability of the geomagnetic field, increases the probability of emergencies during strong geomagnetic storms and substorms.
According to a study Gil et al., 2019[98] on using time series and statistical analysis to determine the association between space weather and electrical grid breakdowns, intense solar phenomena disrupted transmission line productivity in southern Poland. The analyzed telluric field and observed GIC demonstrate a significant dependence on the induction response of the electrically conducting Earth join, according to a study by Sokolova et al., 2019[99] on the correlation between space weather driven geomagnetic and telluric field variability with geoelectric and current induced in electrical grid states. The computed telluric fields exhibit a high connection with the observed GICs in Karelia's and the Kola Peninsula's power transmission lines. Important conclusions about the variability of geomagnetic and telluric fields in the region of central and eastern Fennoscandia connected to the GIC hazard might be drawn from a combined investigation of all three forms of changes. By using observations from the IMAGE magnetic observatories and the station for recording geomagnetically induced currents (GIC) in the electric transmission line in 2015, the study by Vorobev et al., 2019[53] on analysis between variations of geomagnetic field, auroral electrojet, and geomagnetic induced current states examines relationships between geomagnetic field and GIC variations. High-altitude electromagnetic pulses (HEMPs) are bursts of electromagnetic energy in transmission line states, according to a study by Jeong, 2019 [80]. A HEMP is made up of three components: E1, E2, and E3. E1 and E2 are instantaneous emissions that can harm electronic components, whereas E3 causes low frequency geomagnetically generated currents in transmission lines and power transformers. According to a study on GIC phenomena and their impact on power system operation by Bejmert et al., 2020[81], a recorded case of transformer differential protection tripping due to GMD was detected using two algorithms that used rate of change of transformer differential currents and the DC component in the neutral current. To limit the influence of GIC, the two previously deployed methods in the power system either install capacitor neutral blocking on HV transformers or block capacitor banks in the high voltage transmission line.
According to a study Simpson & Bahr, 2020[100] on estimating the electric field response across Scotland using geomagnetic fields, magneto telluric impedances, and perturbation tensors, peak-to-peak electric field magnitudes in some areas of the Scottish Highlands may have reached 13 V/km during the Halloween storm, with line-averaged electric fields bigger than 5 V/km sustained along some long-distance, high-voltage power transmission lines. According to a study Švanda et al., 2020[73] looking for a rapid response of devices in the Czech electric distribution grid to disturbed days of high geomagnetic activity, the anomaly rate increases significantly immediately (within 1 day) after the onset of geomagnetic storms in the case of abundant series of anomalies on power lines. The increase in the anomaly rate is often delayed by 2-3 days in transformers. We also discovered that transformers and some electric substations appear to be vulnerable to substorm exposure, with a delayed increase in anomalies. According to a study Zawawi et al., 2020[7] on the effects of GIC on selected 275 kV sub power system networks in Peninsular Malaysia, which is one of the low latitude countries, long duration with high magnitude GIC is the most hazardous to power transformers and could potentially cause major faults in the power system network. With a value of 315.10, a Neutral Earthing Resistor (NER) can be used to reduce GIC current flow in transmission line and thereby protect the power system network.

E. KEYWORD SUMMARY ON GROUNDING, ELECTRICAL FAULTY AND IMPROVEMENT
According to a study by Divett et al., 2020[101] on calculating the modelled geoelectric field from the spectra of magnetic field variations interpolated from measurements during this storm and ground conductance using a thin sheet model, models to calculate GICs in the transmission network require two steps: I modelling the geoelectric field due to the combined effects of magnetic field variation during a storm and varying ground conductance, and (ii) using a network mode. According to a study Klauber et al., 2020[8] on the consequences of geomagnetically induced currents (GICs) and effective mitigation measures during GMD, ground conductivity models are used to transfer magnetic field data to electric field data.
According to a study by Shu-ming Zhang & Liu, 2020 [71] on installing additional resistors in the transformer neutral points of high-risk nodes to even the GIC distribution in whole networks and make the theoretical calculation of GIC in East China 1000kV power grid after installation, geomagnetic storms and grounding current of DC electrode in converter stations have similar effects in China's 500 kV high-voltage DC network and 800 kV ultra-high voltage DC power transmission system. The study S. M. Zhang & Liu, 2020[67] proposes an evaluation approach based on studied technical criteria for power system safety during geomagnetic storms states that the Earth's electric field is induced on the Earth's surface according to Faraday's law of electromagnetic induction. The potential difference between different grounding points in the power system, because of the Earth's electric field, will drive GIC in the power system, which will flow through the neutral point and winding areas of the power transformer, resulting in saturation of the half wave of the transformer core, resulting in voltage transformation.
According to a study by Abda et al., 2020[70] that reviewed the literature on space weather, geomagnetic disturbances (GMDs), and geomagnetic interference (GICs) and their impacts on power systems in both high and midlow latitude regions, the impact of this complicated interaction causes the magnetic field on the ground to rapidly change. A geoelectric field is induced on the Earth's surface because of this variation, causing a geomagnetically induced current (GIC). The power station/substation nodes are connected by line resistors and earthed through earth ground resistors using line and grounding resistance values provided by Trans power New Zealand Ltd, according to a study by Mukhtar et al., 2020[102] on the calculation of GIC in substations and individual transformers based on geomagnetic activity. According to the calculations for the 2003 storm, GIC more than 10 A may persist for lengthy periods at some spots, causing severe harmonic distortion and maybe localized transformer heating.
According to a study by Caraballo et al., 2020[72] on modelled GIC using a uniform conductivity for the entire Mexican territory and spatially uniform geomagnetic disturbance, the presence of thousands of kilometers of coastal power lines may favor the development of large GIC due to the ground conductivity contrast between the oceans and continental landmass. Haddadi et al., 2021[83] conducted a cross-examination of the outcomes of the loadflow-based (LF), transient stability type (TS), and electromagnetic transient type (EMT) approaches. The goal is to identify their limitations, assess the consistency of their results, and provide assumptions on how to use them for GMD system impacts analysis. The electric field induces an induced voltage in transmission lines, which causes low-frequency (0.1 Hz or lower) Geomagnetically Induced Currents (GICs) to flow through transmission lines and grounded transformers to ground. According to a study by Behdani et al., 2021[75] on the analysis of the power transformer ferro resonance phenomenon due to GICs in series capacitor compensated networks, the effects of various involving parameters such as system loading, compensation level, and substation grounding resistances on the occurrence of ferro resonance due to GICs are evaluated using an example test system in the EMTP-RV environment. The findings show that GICs can significantly increase the vulnerability of power transformers to ferro resonance phenomena in series capacitor compensated power networks. Fig. 9 and Fig. 10 shows the top Scopus and WoS network used by the authors.

F. KEYWORD SUMMARY ON THE ESTIMATION OF THE GIC IN POWER NETWORK
All Based on the Bibliometric study, the study on GIC in power network keep on growing in the form of measurement and calculation. The study in the GIC field started to be explored by middle and low latitude region due to the impact and harmful effect it possesses despites the impact from the GIC is more severe in high latitude region. The study on the GIC based on the simulation and measurement in the power network could benefits in the following ways: • The study on the GIC in Power Network is correlated to the activity of the solar storm and geomagnetic disturbance • The estimation of the GIC is estimated based on simulation and measurement data of the geomagnetic disturbance from the local magnetic field data before comparing with the real-time measurement • The study on the GIC in Power Network is usually linked to the anomalies within the power system such as transformer breakdown, high reactive power, harmonic, and electrical faulty • In Estimating GIC, the purposes are to mitigate the level and threshold of the GIC and finding the possible way to mitigate the level of the GIC which possess harmful effects on the Power System Simplified models of three-phase, five-limb transformer for studying GIC effects The study describes capabilities of a topological model of three-phase, five-limb transformer to accurately represent its response when subjected to geomagnetically induced currents In conclusion, the earliest publication on the study on the GIC in the power network by using the search keyword can be track back since 1979 in Scopus and 1992 in WoS. Based on the Study on GIC in Power Network, the earliest study on the GIC in power network is only perform by the country in high latitude region such as Canada [93], [103], [104] and Finland [105], [106] follow by middle latitude region such as China [3], [107], [108] , Italy [1], [52] and Japan [109]- [112] and low latitude region such as Australia [113], [114] and Malaysia [70], [115] Calculating GIC based on constructing a model of the AC transmission system for quasi-DC frequencies of the GIC, the GICs through transformers can be determined for various geomagnetically induced Earth-Surface-Potentials (ESP) using Electro-Magnetic Transients Program [20]. (EMTP). The study's goal is to discover Harmonics and Switching Transients in the presence of GIC. The transient performance of the Current Transformer (CT) is researched by [26] in order to ascertain the reduced time-to-failure. The relay mis operation existed in two conditions: erroneous CT response and GIC interaction with large power transformers with differential protection, according to saturation from a combination of GIC and DC fault offset. Langlois et al., 1996[116] did a study on the calculation of the GIC at Abiti, Quebec, where they monitored the electric and magnetic fields at a rate of 8640 points per day for 500 days and discovered that the electric fields occur with a probability inversely. The driven GIC software was used in a research by Hannett et al., 1992a [56] to investigate mitigation concepts such as the impacts of line outages, line series capacitors, and transformer neutral blocking resistors. While S. Lu & Liu, 1993[38] used a finite element (FEM) simulation of a transformer to identify geomagnetically induced currents, S. Lu & Liu, 1993[38] utilised a finite element (FEM) simulation of a transformer to identify the geomagnetically induced currents (GIC). The geomagnetically induced currents and local geomagnetic fluctuations were recorded simultaneously at the neighbouring Nurmijarvi Geophysical Observatory, according to a paper by Ari Viljanen, 1998[117] titled Relation of Geomagnetically Induced Currents and Local Geomagnetic Variations. Here are two models for calculating GICs from the magnetic field's time derivative.
The earth's conductivity is used as a fitting parameter in a plane wave model with a homogenous earth. Mckay & Whaler, 2006[118] used magneto telluric (MT) data in the form of MT tensors to estimate the size and spatial distribution of the electric field in northern England and southern Scotland with the goal of predicting the flow of geomagnetically induced currents (GIC) in power networks in the region. According to a study conducted by A Viljanen et al., 2006[119] on the relationship between substorm characteristics and rapid temporal fluctuations of the ground magnetic field, significant dH/dt occur predominantly during the substorm beginning when the amplitude of the westward electrojet rapidly grows. The effects of interactions between stations on the calculation of geomagnetically induced cur-rents in an electric power transmission system R. J. Pirjola, 2010[120]  The GIC level at the Ling'ao nuclear power plant is higher than at the Shanghe substation, according to the statistics. The cause is thought to have something to do with the grid structure and the coast effect. According to a study conducted by Wu et al., 2014[121] to clarify and measure the risk from GMD represented by geoelectric field, method for analysis of relationship between voltage stability of long-distance transmission system and the size and direction of geoelectric field, the results show that the method is feasible, and the index can reflect the relationship between the long-distance transmission system voltage stability and the geoelectric field, and the set of the indices. Reliable estimates are obtained, and the modelling are found to explain up to 90% of the measurements, according to a study conducted by Püthe et al., 2014[122] from Switzerland on 3-D modelling of induction processes in a heterogeneous Earth and the construction of a magnetospheric source model described by low-degree spherical harmonics from observatory magnetic data to calculate GIC.
According to a study conducted by M. Nakamura et al., 2015 [48] on statistical estimation of extreme aurora electrojet activities, statistical evidence for finite upper limits to AL and AU, estimate the annual expected number and probable intensity of their extreme events, and detect two different types of extreme AE events is an important factor in space weather research. The new technique helps mitigate the zero sequence current flowing through the neutral of transformers during unsymmetrical faults, according to a study by Hussein & Ali, 2016[50] from the United States on a new approach by using a controlled resistance to suppress the GIC flowing through the neutral of transformers. The preliminary electric field predictions of studied by Bonner & Schultz, 2017[123] are compared to previously recorded time series, idealised transfer function scenarios, and existing industrial data. Some limitations, such as long period diurnal drift, are addressed, and solutions are suggested to further improve the method before direct comparisons with actual GIC measurements are made, according to -try methods to assess the validity of the algorithm for potential adoption by the power industry. In recent years, there has been a lot of progress in the research of GIC in Power Networks. Table VIII shows some of the latest study on the GIC in the Power Network.

G. FUTURE TREND
All The field of ''Estimation of the GIC in the Power Network" have been adopting 3D earth conductivity model to replace the 1D conductivity model as it is more accurate and efficient in estimating the GIC level. There is also the research on time-series and statistical analysis study on the failure of the electrical equipment due to GIC. This method involves identifying the time of the GMD impact and the time it takes to cause the breakdown to the electrical equipment from the Power System Network. There is also the study on impact of the High-Altitude Electromagnetic Pulses (HEMPs) on the formation of the GIC in Korean Electric Power System which is new to the field. There is also the study on the delay action of the exposure of the power grid due to the strong geomagnetically induced current. Looking at the current scenario, this trend is expected to expand shortly and studied in various countries to identify the threshold limit of the GIC on the power network. The latest study provides the possibility of identifying the reason behind the electrical equipment failure in the power network by applying time-series analysis, improved the calculation method on the GIC by using 3D ground conductivity, and study any related impact which might generate backflow current from the underground other than the impact from the GMD such as HEMPs.

VI. CONCLUSION
This paper is a unique collection of the bibliometric study and recent development in the field of ''Estimation of the GIC in the Power Network". Bibliometric study helped to discover the hidden structures of the publications in this area.  work in Scopus is produced in Engineering and Energy discipline while WoS is Engineering and Meteorology Atmospheric Sciences. Space Weather is the journal with maximum publication followed by IEEE Transactions on Power Delivery.
The United States remains at the top position for Scopus and WoS in terms of number of publications in country wise analysis. In the Institution wise analysis, North China Electric Power University stands at the top in Scopus and Finnish meteorological institute remains at top in WoS. Then, the comparative analysis of ''Estimation of the GIC in the Power Network" domain is performed from the context of the most influential papers in this field. This analysis could provide a clearer and better perspective for the new researchers. Research works on "GIC" has evolved over the years as it can be seen from the indexing by Scopus and WoS. Till now (from 2009), there are 2094 publications in "GIC" as indexed by Scopus and 809 publications indexed by WoS.
These publications have received a total of 26937 citation in Scopus and 11749 citations for WoS, which specifies the significance and wider acceptability of the "GIC" domain. However, in the case of ''Estimation of the GIC in the Power Network" publications, there are only 601 and 357 for Scopus and WoS publications with only 7862 citation counts for Scopus and 4761 citation count for WoS. Fig. 11 shows the respective comparison between the publications and citations count of "GIC" and ''Estimation of the GIC in the Power Network". We can observe that there is a huge gap between the publications on general "GIC" research and ''Estimation of the GIC in the Power Network" research. Therefore, one of the major limitations of this study is the available numbers of papers in ''Estimation of the GIC in the Power Network". However, this also limelight's the immense scope and need for more and more research in the domain of ''Estimation of the GIC in the Power Network". The future scope of this study may entail the more depth analysis with other indexing databases such as GIC effect on pipeline system.

ACKNOWLEDGMENT
For the opportunity to participate in this research, the author would like to thank the College of Engineering, Universiti Teknologi MARA (UiTM), the members of the Centre for Satellite Communication, and Tenaga Nasional Berhad (TNB). We'd also like to express our gratitude to the UiTM's Financial Support for funding the project. VOLUME XX, 2022 Kharismi Burhanudin is a student at Universiti Teknologi MARA, Malaysia and currently pursuing his PhD and conducting research on space weather perturbation impact on geomagnetic induced current (GIC) at the Malaysian Power Network. He received the master's and bachelor's degree from the same University.