Earth Currents Research Articles

Improving the distribution system capability by incorporating ZnO nanoparticles into high-density polyethylene cable materials

This paper introduces a novel insulated cable designed to enhance the distribution system’s capabilities. Accordingly, high-density polyethylene loaded with varying concentrations of zinc oxide (ZnO) nanoparticles (NPs) ranging from 0.0 to 5 wt% was prepared using the melt-blending technique. Zinc oxide (NPs) is synthesized by using sol–gel technique and their microstructure was examined by X-ray diffraction. The new insulated cable, HDPE nanocomposite loaded with 1 wt% of ZnO, demonstrates a 43% reduction in the relative dielectric constant and a 16.5% improvement in breakdown strength compared to pure HDPE. The observed changes in both the dielectric constant and breakdown strength offer several advantages in electrical applications. These benefits include a decrease in feeder current at the same loading level, mitigation of inrush transients during load switching, and a reduction in earth fault current values, particularly in unearthed distribution networks with ungrounded cables. A comparative study is conducted between the conventional insulating cable based on the original material (HDPE) and the new insulated cable incorporating ZnO nanomaterial at a ratio of 1.0 wt% of the total cable mass per unit length. This comparison utilizes data from two actual medium-voltage distribution feeders. Both actual feeders are simulated using the EMTP/ATP package. The obtained results prove the efficacy of the developed material cable (polymer doped with ZnO NPs) compared to the base material. The peak and duration of inrush current can be cut to 77.3% and 67% of their original values, respectively. The earth fault current can be reduced to 56.5% in ungrounded networks, while substation current under the normal operation can be cut to 84.3% with the same load currents.

Engineering problems of restoration. Protection of historic buildings from negative environmental impact

The relevance of the study is due to the problem of preservation of historical and cultural heritage of Russia and the city of Tomsk in particular.Purpose: The aim of the paper is to draw attention to the disturbance of the structural integrity of architectural monuments such as transport vibrations and stray earth currents.Methodology/approach: Field studies of the architectural monument of the Church of St. Alexander Nevsky in Tomsk; the analysis of the city plan in the area of Gertsen and Sovetskaya Streets; measures proposed for the monument protection from negative influences of the urban environment. Originality: The paper proposes protection measures for the Church of St. Alexander Nevsky of the regional importance from vibrations and stray earth currents generated by trams moving in the vicinity of the Church.Practical implications: Recommendations are given for eliminating the negative impact of transport vibrations on architectural monuments on the example of the Church of St. Alexander Nevsky in Tomsk.

Влияние космической погоды на надежность функционирования транспортных систем на высоких широтах

The review offered for the first time in the Russian scientific literature is devoted to various aspects of the problem of the impact of space weather on ground transport systems. An analysis of available information indicates that space weather disturbances can affect rail infrastructure through both direct and indirect effects on system components. One of the main hazards is geomagnetically induced currents (GICs) in grounded extended structures excited by the geomagnetic field disturbances. The telluric electric fields and currents associated with them can cause power outages and malfunctions in the railway automation track circuits. Indirect impact is possible through disturbances in the stable supply of electricity, disturbances in communication systems and in the appearance of positioning errors in global navigation satellite systems. The review provides information necessary for engineers of transport and energy systems about the main factors of space weather that could pose a threat to such systems. Examples of the influence of geomagnetic disturbances on the automatic signaling of the northern sections of Russian Railways are given. The prospects for monitoring space weather and the aurora oval for the needs of Russian Railways are discussed.

Evaluation of telluric-associated corrosion on buried pipelines

Telluric currents, often known as geomagnetically induced currents (GIC), are produced by the natural variations of the Earth's magnetic field.The corrosion protection system of a buried pipeline generally comprises the coating and cathodic protection system. Cathodic protection is an electrochemical protection system that maintains the pipe-to-soil potential (PSP) sufficiently negative in order to reduce corrosion to negligible levels. Varying telluric currents alter the PSP, thus interfering with the pipeline corrosion protection system and can create conditions when corrosion might increase above acceptable levels.This paper presents an evaluation of telluric-associated corrosion derived from measured and modelled PSP variations. The corrosion rates (metal loss per year) due to varying telluric currents with continuous frequency spectra (1 Hz–10−5 Hz) are approximated with the use of published experimental results derived for the specific sets of fixed frequencies.Results are presented for PSP observed on Australian and European pipelines during two periods of strong geomagnetic activity (in 2003 and 2004) and for identical hypothetical pipelines located at different latitudes for the entire year 2004.From the analysis of recorded PSP, it was found that the corrosion rates for a near-equatorial pipeline (Australia) could be higher than for mid-latitudes (Europe). This is possible because telluric-associated corrosion rates depend not only on geomagnetic activity, but on the properties of the pipeline coating, the performance of the cathodic protection system and environmental conditions.The study demonstrated that without cathodic protection the estimated corrosion rates exceeded the benchmark values recommended by national and international standards, and in exceptional case can exceed the acceptable values even with cathodic protection.Telluric-associated corrosion estimated for the identical hypothetical pipelines located in zones with different geomagnetic activity, clearly demonstrated the latitudinal dependence. The substantial increase of corrosion rates (about 5 times) has been found with increase of latitude from subauroral to auroral locations.

Experience in Registering Higher Harmonics of Industrial Frequency Currents on a Stand for Measuring Telluric Currents

Experience in Registering Higher Harmonics of Industrial Frequency Currents on a Stand for Measuring Telluric Currents

Telluric Currents Generated by Solar Flare Radiation: Physical Model and Numerical Estimations

The current studies of solar-terrestrial relations and possible impact of space weather on the seismic activity are based on statistical analysis without detailed consideration of possible physical mechanism that results in fuzzy and contradictory conclusions. We propose to consider a hypothesis of electromagnetic earthquake triggering by a sharp rise of telluric currents in lithosphere including crust faults due to interaction of solar flare X-ray radiation with ionosphere-atmosphere-lithosphere system resulted in a rise of telluric currents in the crust faults. This hypothesis is based on field and laboratory experiments carried out in Russia within the last forty years and clearly demonstrated a possibility of earthquake triggering by electric current injected into the fault. We developed a mathematical model and computer code for numerical estimations of telluric currents generated by solar flare radiations. The obtained numerical results demonstrate that solar flares can cause variations in the density of telluric currents in the crust faults, comparable to the current densities generated in the Earth’s crust by artificial pulsed power sources capable to trigger earthquakes. Consequently, the triggering of seismic events is possible not only by artificial sources of electric current, but also by ionospheric disturbances caused by strong solar flares.

Experience in registering higher harmonics of industrial frequency currents on a stand for measuring telluric currents

Experience in registering higher harmonics of industrial frequency currents on a stand for measuring telluric currents

Complete Method to Assess the DC Corrosion Impact on Pipeline Systems During the Planning and Approval Stages of HVDC Systems With Earth Current Return

The technology of HVDC systems defines the current return process, which can be through a dedicated metallic conductor or through a conducting medium, such as the earth or sea. Although the magnitude of the earth/sea return current is normally specified in local regulations or project specifications, there is no explicit methodology to estimate the intermittent, time duration of this current, over the life-span of a system. However, dc interference/corrosion impacts related to the development of HVDC links are, to a large extent, associated to the time duration of the earth current. In the absence of any explicit methodology, the potential influence of the earth/sea return current on nearby critical infrastructures is often based on unrealistic or on conservative interference impact studies. The purpose of this paper is to firstly provide a methodology to quantify the expected intermittent duration of the earth return current - in point-to-point bipolar HVDC systems, which arises from their partial-availability or the emergency conditions. Subsequently, the proposed methodology is applied in a realistic dc interference/corrosion study of a critical pipeline system that operates near a HVDC link currently being constructed. In essence, the paper describes a top-down complete approach for HVDC dc interference modelling endeavors in an attempt to avoid conservative and costly mitigation measures concerning third-party critical infrastructures in the nearby vicinity.

Гидрологические исследования в северо-восточной части Баренцева моря в 2019 и 2020 г

The article presents the results of hydrological studies of the north-eastern part of the Barents Sea. The observations were made in the oceanographic expeditions R/W “Dalnie Zelentsy” of the MMBI RAS in October–November 2019 and 2020. The analysis of a series of hydrological sections is carried out, which details the vision of the structure of the waters and currents of the studied area. In the water structure, two streams of Atlantic waters are distinguished. The flows are directed opposite to each other and are located in different deep layers. The Atlantic stream emerging from the Barents Sea is identified as a branch of the warm New Earth current. At the beginning of the winter,the current spreads in a layer from the surface to 50–75 m. The Atlantic waters flowing into the Barents Sea are identified as a branch of the deep current of the St. Anna trench. They come from the Polar Basin and pass into the sea from east to west up to 62–60o E.

HARDWARE-SOFTWARE COMPLEX FOR THE TELLURIC CURRENT INVESTIGATION IN A SEISMICALLY HAZARDOUS REGION OF ZAILIYSKY ALATAU

To solve the current issues of detecting seismoelectric signals at preparing earthquakes, a hardware-software complex was created, designed to study the telluric current variation in the ultra-low frequency range (0-20 Hz), which is installed in the seismically active region of the Zailiysky Alatau (Northern Tien Shan) near the foci of the Vernensky M7.3 and Keminsky M8.2 catastrophic earthquakes. Special mathematical algorithms and program tools were designed for continuous registration, real-time data analysis, and visualization of the information on telluric current. It was proposed an effective system for reducing the influence of stray currents on the measuring equipment, an optimal lightning protection scheme, and a grounding system for the power supply devices, which allow uninterrupted measurements in mountain conditions even in time of close intensive thunderstorm. The capabilities of the hardware-software complex make it possible to detect both the weak electric signals with an amplitude of several tens–hundred of microvolts only, and intensive electromagnetic pulses from close lightnings without the damage of registering apparatus. In the records of telluric current the wave oscillations were detected which belong to the frequency range of the Pc2–Pc4 class micropulsations of the geomagnetic field. Perspectives of the detection of seismogenic electrical signals in variations of telluric current on the eve and during earthquakes are connected with data obtained during the earthquake of magnitude MPV 4.5, which occurred on July 1, 2021 at 60.4 km from the measuring point. At the time of the earthquake, immediately after the main shock, in conditions of good weather and low industrial noise, using the calculation of the dynamic power spectrum of the telluric current in the frequency range 0.2 Hz - 0.0282 Hz, electrical signals were detected, presumably of seismogenic origin.

Revisiting the Predictability of the Haicheng and Tangshan Earthquakes

We analyze a set of precursory data measured before but compiled in retrospect of the MS7.5 Haicheng earthquake in February 1975 and the MS7.6–7.8 Tangshan earthquake in July 1976. We propose a robust and simple coarse-graining method that aggregates and counts how all the anomalies together (levelling, geomagnetism, soil resistivity, earth currents, gravity, earth stress, well water radon, well water level) develop as a function of time. We demonstrate strong evidence for the existence of an acceleration of the number of anomalies leading up to the major Haicheng and Tangshan earthquakes. In particular for the Tangshan earthquake, the frequency of occurrence of anomalies is found to be well described by the log-periodic power law singularity (LPPLS) model, previously proposed for the prediction of engineering failures and later adapted to the prediction of financial crashes. Using a mock real-time prediction experiment and simulation study, based on this methodology of monitoring accelerated rates of physical anomalies measured at the surface, we show the potential for an early warning system with a lead time of a few days.

Study on the ULF Magnetic Field Generated by Earth Currents Relating to Large EQs

AbstractULF magnetic anomalies (f < 1 Hz) have been observed prior to multiple large earthquakes (EQs) during the last three decades. A polarization analysis method was produced and applied in many EQ cases in order to discriminate the weak ULF crustal signals from other signals. Although many publications considered the parameter of polarization ratio (amplitude or power ratio of vertical magnetic field component to horizontal components), a key parameter in the polarization analysis method, useful to detect the possible magnetic signals associated with EQs, there were also many doubts on its reliability. The aim of this work is to evaluate the possibilities of the polarization ratio increases prior to large EQs based on the prevail assumption of Earth currents as the source of ULF emissions during the early stage of EQ preparation independent of the mechanism involved in producing the currents, and the parallel 3‐D finite‐difference time‐domain technique is applied to calculate the electromagnetic responses in the whole inhomogeneous Earth‐ionosphere waveguide. The contributions of the lightning discharges on ULF power are also evaluated based on the gridded flash counts included in the Lightning Imaging Sensor climatology data. The results reveal that the surface vertical magnetic field and polarization ratio are possible to increase locally around the epicenters as long as the intensity of the surface seismic magnetic fields are large enough compared with those produced by other sources. Unfortunately, the actual increases are usually difficult to be distinguished obviously mostly due to the weak seismic increases.

Behavior of Residual Current Devices at Frequencies up to 50 kHz

The use of residual current devices (RCDs) is obligatory in many types of low-voltage circuits. They are devices that ensure protection against electric shock in the case of indirect contact and may ensure additional protection in the case of direct contact. For the latter purpose of protection, only RCDs of a rated residual operating current not exceeding 30 mA are suitable. Unfortunately, modem current-using equipment supplied via electronic converters with a pulse width modulation produces earth fault currents composed of high-frequency components. Frequency of these components may have even several dozen kHz. Such components negatively influence the RCDs’ tripping level and, hence, protection against electric shock may be ineffective. This paper presents the results of the RCDs’ tripping test for frequencies up to 50 kHz. The results of the test have shown that many RCDs offered on the market are not able to trip for such frequencies. Such behavior was also noted for F-type and B-type RCDs which are recommended for the circuits of high-frequency components. Results of the test have been related to the requirements of the standards concerning RCDs operation. The conclusion is that these requirements are not sufficient nowadays and should be modified. Proposals for their modification are presented.

Contribution to the Research of the Effects of Etna Volcano Activity on the Features of the Ionospheric Total Electron Content Behaviour

This research represents a contribution to the theory on the coupling of the volcanic activity and the ionospheric dynamics, represented by total electron content (TEC) patterns and their behaviour. The ionospheric response to the activity of the Etna volcano has been analysed using global navigation satellite system (GNSS)-derived TEC values, employing data from International GNSS Service (IGS) reference station near the volcano and on two distant IGS locations. Volcanic activity has been modelled using volcanic radiative power (VRP) data obtained by the Middle InfraRed Observation of Volcanic Activity (MIROVA) system. The estimated minimal night TEC values have been averaged over defined index days of the VRP increase. During the analysed period of 19 years, the volcano activity was categorised according to pre-defined criteria. The influence of current space weather and short-term solar activity on TEC near the volcano was systematically minimised. The results showed mean/median TEC increases of approximately +3 standard deviations from the overall mean values, with peak values placed approximately 5 days before the VRP increase and followed by general TEC depletion around the time of the actual volcanic activity increase. Additionally, TEC oscillation pattern was found over the volcano site with a half-period of 6.25 days. The main interpretation of results indicates that the volcanic activity has modified the ionospheric dynamics within the nearby ionospheric region before the actual VRP increase, and that the residual impact in the volcano’s surrounding area refers to terrestrial endogenous processes and air–earth currents. Those changes can be detected during criteria predefined in the research: during quiet space weather conditions, observing night-time TEC values and within the limits of low short-term solar influence.

Harmonic Current Distribution in Grounding Systems of Cabled Medium Voltage Grids during Single-Pole Ground Fault

The design of every power supply system must guarantee the safety for human life even in the event of a fault. Due to the system change in the electrical power supply, the fault current contains more and more unknown shares of current harmonics. Especially in medium voltage grids, which are operated with resonant grounding, these are determining for the level of the single-pole ground fault current for determination of permissible touch voltages and compliance with the normative requirements of the European standard EN 50522 must therefore be re-evaluated. In its first part, this concept paper presents the frequency dependent principles of earth loops formed by the grounding system. The focus here is on cabled grids and the influence of connected structures of the low voltage grid. The second part deals with the superposition of these loop currents and the resulting earth currents in case of a line to ground fault. The authors address explicitly the frequency dependence of the current distribution and describe the expected behaviour for current harmonics. The proposed approaches result from processing the state of knowledge, research work and the evaluation of several measurements. The aim is to develop an understanding of the influence of the components connected to a grounding system and to derive generally applicable principles. Therefore, the authors present the results of recent measurements in the last part of the handed paper and point out the possibilities and limits of modeling. It is shown that a dedicated treatment of harmonic currents in the case of a single-pole fault is possible with the methods described. This allows these to be neglected in the estimation of touch voltages under specified circumstances, saving costs for the assessment of grounding systems.

Monitoring of Gas Emissions in Light of an OEF Application

This study analyzes the possibility to use geophysical and geochemical parameters in an OEF (Operational Earthquake Forecasting) application correlated with short-term changes in seismicity rates using a magnitude–frequency relationship. Tectonic stress over the limits of rock elasticity generates earthquakes, but it is possible that the emission of gases increases as a result of the breaking process. The question is how reliable is the emission of radon-222 and Carbon Dioxide (CO2), with effects on air ionization and aerosol concentration, in an OEF application? The first step is to select the seismic area (in our study this is the Vrancea area characterized by deep earthquakes at the bend of the Carpathian Mountains), then determine the daily and seasonal evolution of the forecast parameters, their deviations from the normal level, the short-term changes in seismicity rates using a magnitude–frequency relationship and finally to correlate the data with recorded seismic events. The results of anomaly detection, effect evaluation and data analysis alert the beneficiaries specialized in emergency situations (Inspectorate for Emergency Situations, organizations involved in managing special events). Standard methods such as the standard deviation from the mean value, time gradient, cross correlation, and linear regression are customized for the geological specificity of the area under investigation. For detection we use the short-time-average through long-time-average trigger (STA/LTA) method on time-integral data and the daily–seasonal variation of parameters is correlated with atmospheric conditions to avoid false decisions. The probability and epistemic uncertainty of the gas emissions resulting from this study, in addition to other precursor factors such as air ionization, time between earthquakes, temperature in the borehole, telluric currents, and Gutenberg Richter “a-b” parameters, act as inputs into a logical decision tree, indicating the possibility of implementing an OEF application for the Vrancea area. This study is novel in its analysis of the Vrancea area and performs a seismic forecasting procedure in a new form compared to the known ones.

Space weather and earthquakes: possible triggering of seismic activity by strong solar flares

The studies completed to-date on a relation of the Earth’s seismicity and solar processes provided the fuzzy and contradictory results. The main problem of this research is a lack of physical explanation of a mechanism of earthquake triggering by strong variations of space weather conditions. Based on results obtained in the field and laboratory experiments on earthquake triggering by DC pulses injection into the Earth crust we may assume that the similar triggering phenomena may occur after the strong electromagnetic impact to the earthquake source due to solar flares or geomagnetic storms. Numerical estimations demonstrated that telluric currents induced by geomagnetic pulsations generated by solar flare have the similar density at the depth of earthquake source location (10-6 A/m2) in comparison with the current density generated by artificial power sources (10-7 – 10-8 A/m2) resulted in observed spatiotemporal redistribution of seismic activity in the regions of Pamirs and Northern Tien Shan. For supporting the idea of a possible earthquake triggering by solar flares we carried out a statistical analysis of global and regional (Greece) seismicity behavior during the solar flare of X9.3 class occurred on September 6, 2017 (the strongest flare over the past thirteen years). We have discovered a new evidence of earthquake triggering due to the Sun-Earth interaction by simple comparison of a number of earthquakes before and after the strong solar flare. The global number of earthquakes (USGS catalog, M ≥ 4) for time window of ±11 days after the solar flare has increased by 68%, and the regional seismicity (Greece, EMSC catalog, M ≥ 3) has increased by 120%.

Induced currents due to 3D ground conductivity play a major role in the interpretation of geomagnetic variations

Abstract. Geomagnetically induced currents (GICs) are directly described by ground electric fields, but estimating them is time-consuming and requires knowledge of the ionospheric currents and the three-dimensional (3D) distribution of the electrical conductivity of the Earth. The time derivative of the horizontal component of the ground magnetic field (dH∕dt) is closely related to the electric field via Faraday's law and provides a convenient proxy for the GIC risk. However, forecasting dH∕dt still remains a challenge. We use 25 years of 10 s data from the northern European International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer network to show that part of this problem stems from the fact that, instead of the primary ionospheric currents, the measured dH∕dt is dominated by the signature from the secondary induced telluric currents at nearly all IMAGE stations. The largest effects due to telluric currents occur at coastal sites close to high-conducting ocean water and close to near-surface conductivity anomalies. The secondary magnetic field contribution to the total field is a few tens of percent, in accordance with earlier studies. Our results have been derived using IMAGE data and are thus only valid for the stations involved. However, it is likely that the main principle also applies to other areas. Consequently, it is recommended that the field separation into internal (telluric) and external (ionospheric and magnetospheric) parts is performed whenever feasible (i.e., a dense observation network is available).

Long-period (10 < T < 20,000 s) Magnetotelluric Studies in Northern Vietnam

Abstract —We consider results of magnetotelluric and magnetovariational soundings in the period range 10 < T ≪ 20 000 s in the North Vietnam area. The simple structure of magnetovariational responses is shown, which generally reflects the electrically conductive quasi-two-dimensional structure of the Earth’s crust. Impedance responses form as a superposition of responses of local complex subsurface and quasi-two-dimensional regional deep-seated structures. Separation of local and regional effects made it possible to construct a geoelectrical depth model of the regional tectonosphere, whose main elements are electrically conductive subvertical trans-lithospheric faults and high-resistivity disturbances of the conductive asthenosphere. These elements, favoring the flow of telluric currents induced in deep-seated electrically conductive systems into the sedimentary cover, form zones of abnormal apparent-resistivity curves. The apparent resistivity monotonously increases with increasing the period up to 20,000 s. We called the combination of such elements of the geoelectrical model a ultradeep fluid–fault system (UDFFS). The modeling has established the location of three orthogonally intersecting UDFFS of NE and SE strikes in the North Vietnam area. It shows that conductive (fluid-saturated) translithospheric faults extending to the base of the sedimentary sequence control the location of petroleum fields and ore deposits. A method for separating local and regional magnetotelluric effects is proposed. It permits one to determine reliably the main strikes of a regional two-dimensional structure and the configuration of the apparent-resistivity curves along them.

Seismoelectric effect in Lamb’s problem

Seismoelectric effect is studied in the framework of classical Lamb’s problem with impulse or time- variable mechanical action on an elastic porous half-space. Radiation of elastic waves gives rise to pressure variation of groundwater fluid contained in pores and cracks. This causes the generation of telluric electric fields and currents due to the seismoelectric effect. A diffusion type equation is applied to describe the variations of the pore pressure and telluric electric field. Particular emphasis has been placed on the properties of seismoelectric signals caused by Rayleigh wave propagation since this wave has maximal amplitude at a considerable distance from the seismic source. For practical purposes and geophysical application, the co-seismic phenomena related to seismoelectric effect are examined in more detail.