Earth Currents Research Articles

Effect of the electromagnetic environment in pipes in Yakutia

The results of measurements of telluric currents flowing through pipelines laid in the cryolithozone in Yakutia are presented during geomagnetic storms and lightning discharges occurring in the 10 km zone around the pipeline. The currents reach tens of amperes. Construction of a lightning density distribution map. The effect of a direct current flowing in a 150 m long pipeline with a diameter of 110 mm laid in permafrost on the change in the pipe-to-ground potential is measured. Based on the analysis of variations in the horizontal component of the magnetic activity in the current 24th cycle of solar activity, it is established that the frequency of occurrence of a certain level of the rate of change in geomagnetic activity can be expressed by a power law with an order of magnitude of about two at low values. The exponent decreases to unity as the geomagnetic activity increases. The probability of occurrence of time intervals with given threshold values of the rate of change of geomagnetic activity is determined.

Tidal influence on self‐potential measurements

AbstractLong‐term surface and borehole self‐potential (SP) monitoring was conducted in the UK Chalk aquifer at two sites. The coastal site is ~1.7 km from the coast, and the inland site is ~80 km from the coast. At both sites, power spectral density analysis revealed that SP data contain the main ocean tidal periodic components. However, the principal lunar component (M2), the dominant ocean tidal component, was most significant at the coastal site. The M2 signal in surface‐referenced SP data at the inland site was partly due to telluric currents caused by the geomagnetic ocean dynamo. Earth and/or atmospheric tides also contributed, as the SP power spectrum was not typical of a telluric electric field. The M2 component in borehole‐referenced data at the inland site was below the significance level of the analysis method and was 2 orders of magnitude smaller than the M2 signal in borehole‐referenced SP data at the coastal site. The tidal response of the SP data in the coastal borehole is, therefore, primarily driven by ocean tides. These cause changes in fluid pressure and chemical concentration gradients within the coastal aquifer, leading to time varying electrokinetic and exclusion‐diffusion potentials. Borehole‐referenced SP measurements could be used to characterize and monitor tidal processes in coastal aquifers such as the intrusion of seawater.

Effects of the March 2015 solar eclipse on near-surface atmospheric electricity.

Measurements of atmospheric electrical and standard meteorological parameters were made at coastal and inland sites in southern England during the 20 March 2015 partial solar eclipse. Clear evidence of a reduction in air temperature resulting from the eclipse was found at both locations, despite one of them being overcast during the entire eclipse. The reduction in temperature was expected to affect the near-surface electric field (potential gradient (PG)) through a reduction in turbulent transfer of space charge. No such effect could be unambiguously confirmed, however, with variability in PG and air-Earth current during the eclipse being comparable to pre- and post-eclipse conditions. The already low solar radiation for this latitude, season and time of day was likely to have contributed to the reduced effect of the eclipse on atmospheric electricity through boundary layer stability. The absence of a reduction in mean PG shortly after time of maximum solar obscuration, as observed during eclipses at lower geomagnetic latitude, implied that there was no significant change in atmospheric ionization from cosmic rays above background variability. This finding was suggested to be due to the relative importance of cosmic rays of solar and galactic origin at geomagnetic mid-latitudes.This article is part of the themed issue 'Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse'.

Comparison of auroral ionospheric and field‐aligned currents derived from Swarm and ground magnetic field measurements

AbstractDerivation of the auroral ionospheric currents from magnetic field measurements can produce drastically different results depending on the data and method used. We have cross tested several methods for obtaining instantaneous field‐aligned and horizontal currents from Swarm satellite and International Monitor for Auroral Geomagnetic Effects (IMAGE) ground magnetic field measurements. We found that Swarm can yield latitude profiles of the east‐west component of the divergence‐free current density at most at ∼200 km resolution, typically resolving the electrojets. The north‐south divergence‐free component, on the other hand, is not always well reproduced due to the small longitudinal distance between the side‐by‐side flying satellite pair. Swarm can yield the field‐aligned and curl‐free current density at a wider range of latitude resolutions (∼7.5–200 km) than the divergence‐free current density. While 7.5 km is suitable for comparison with auroras, 200 km typically resolves the Regions 1 and 2 field‐aligned currents. IMAGE can yield maps of the divergence‐free current density at ∼50 km resolution. Induced telluric currents should be accounted for in the derivation. Not accounting for them in the Swarm analysis, however, does not appear to introduce significant errors. Ionospheric conductances can be estimated by combining the total horizontal current density, consisting of the curl‐free and divergence‐free components, with the electric field measurements. Our results indicate that Swarm can only yield these at ∼200 km scale size when there is no significant dependence on longitude. However, combining the divergence‐free current from IMAGE with the curl‐free current and electric field from Swarm could yield conductance maps at ∼50 km resolution.

Potential Compensation Method for Restraining the DC Bias of Transformers During HVDC Monopolar Operation

The earth return currents (ERCs) of high-voltage direct current transmission can cause severe half-cycle saturation of transformers. This study presents a novel and highly beneficial potential compensation method (PCM) to mitigate the detrimental effects of ERCs. The simulation model of the PCM was first derived and verified through a laboratory test. Analysis has suggested an association of network configuration and mutual resistance to the compensatory factor. The proposed method has been applied in two representative substations with different types of transformers in various operating modes. Results show that as opposed to the neutral blocking device (NBD), the PCM can adjust the dc voltage equilibrium of ac systems rather than intervene in the neutral path of transformers. Moreover, the PCM can eliminate the direct magnetomotive force of autotransformers with proper selection of the injected current. An application shows that the PCM can outperform NBDs and line-series capacitors in restraining the dc bias of autotransformers.

Shore-to-Ship Power

This contribution starts with a review of the state of the art of existing high-voltage shore connection (HVSC) systems in terms of principles, rules, publications, technologies, and relevant installations. Then, tutorial sections present the main technical aspects of HVSC systems as ship-to-shore interface, shore equipment (transformers, converters, etc.), onboard devices (cubicles, shore switchboard, etc.), operating sequences, and feasibility aspects, for both commercial and military applications. Finally, some technical challenges are presented, concerning intentional/unintentional bonding, interactions between HVSC bonding and cathodic protection systems, bonding opportunity, and electrical safety aspects related to bonding issues in case of large earth fault currents in port facilities.

North America Does the Wave (Slowly)

Data-driven modeling helps explain how convection currents in Earth's mantle influence the rise and fall of surface features, but these models are in an early stage.

Determining the efficiency of the compensation of single-phase capacitive earth currents using arc-suppression coils of different designs implemented in an experimental workbench

Results of the experimental comparison of the compensation of single-phase capacitive earth currents using arc-suppression coils of two cardinally different designs, i.e., plunger-type coils and coils controlled by magnetic bias, are presented. It was previously shown using the simple formula and the calculation grid model that the response time of the reactors determined through the time required to compensate the power component of the earth current depended on the phase angle of the voltage at the moment of earth fault [1]. If the earth fault occurs not at the moment of the maximum voltage, an aperiodic component appears in the coil current, which makes it impossible to compensate instantaneously the capacitive earth current. An experimental workbench with a voltage of 6 kV used to carry out the measurements is described. The measurement results show that the coils of both designs have similar response times, which are on average of the order of a few hundreds of milliseconds; these values substantially exceed the implied values of the response time of the coils. It is shown that the response time of the coils cannot be the criterion for their efficient operation. Therefore, to compensate for an intermittent arc capacitive earth fault, a comparative criterion for assessing the efficiency of the operation of the coil is proposed, which is based on the average value of the energy dissipated the site of fault.

New Insights into Currents in Earth's Magnetic Field

Multisatellite missions give scientists a more complete view of the intense currents that bounce back and forth along our planet's magnetic field lines.

Proximity Effect on the Induced Geoelectric Field at the Lateral Interface of Different Conductivity Structures During Geomagnetic Storms

AbstractThe induced geoelectric fields and telluric currents generated during geomagnetic storms will be distorted by lateral variations of the Earth conductivity. The Galerkin finite element method (FEM) is a useful tool to analyze complicated electromagnetic field problems. In this paper, a uniform thin sheet current with infinite width located at 100 km above the Earth's surface is assumed to represent the source of geomagnetic variations. It is harmonic with the amplitude of 1 A/m at different frequencies. Three Earth conductivity structures are modelled where the basic model is horizontally uniform for comparisons. The second and third structures have the same exact thicknesses and conductivity values with the basic one on one side and five times greater or lower values on the other side to represent conductivity variation from low to high and from high to low. The computational results show that the abrupt changes of conductivities have influences on the induced telluric currents, which can be classified as the proximity effect and the skin effect. For GIC research in power systems, especially in systems located at coastal areas, the geoelectric field and GIC should be determined taking the directions of the transmission lines and of the coast into consideration. Both the proximity effect and the skin effect should be considered along with the coast effect in research of GIC impacts during geomagnetic disturbances. Boundary conditions discussed in this paper can be varied depending on different modelling techniques and on the scales of conductivity structure models.

An Approach to Model Earth Conductivity Structures with Lateral Changes for Calculating Induced Currents and Geoelectric Fields during Geomagnetic Disturbances

During geomagnetic disturbances, the telluric currents which are driven by the induced electric fields will flow in conductive Earth. An approach to model the Earth conductivity structures with lateral conductivity changes for calculating geoelectric fields is presented in this paper. Numerical results, which are obtained by the Finite Element Method (FEM) with a planar grid in two-dimensional modelling and a solid grid in three-dimensional modelling, are compared, and the flow of induced telluric currents in different conductivity regions is demonstrated. Then a three-dimensional conductivity structure is modelled and the induced currents in different depths and the geoelectric field at the Earth’s surface are shown. The geovoltages by integrating the geoelectric field along specific paths can be obtained, which are very important regarding calculations of geomagnetically induced currents (GIC) in ground-based technical networks, such as power systems.

Possible influence of telluric current on seismicity of the Earth’s crust in seismoactive zones

A physical model is proposed for the possible effect of telluric currents on macrofracturing in the Earth’s crust and the triggering of earthquakes via the interaction of telluric currents with the geomagnetic field. For implementation of the considered processes, a an escalated regime due to positive feedback between the decrease in electrical conductivity of the developing earthquake source and the increases in current and pressure in this source was established. Estimates of characteristic earthquake-triggering time that agree with the experimental data were obtained. The model explains the interrelationship between some observed electromagnetic phenomena and earthquake development processes in seismoactive zones.

Corrosive influence of natural geoelectric currents

A brief descriptions of natural geoelectric currents emancipating from earth's core, induced by ionospheric currents, magnetic crochets, magnetic storms, tidal movements and local earth currents due to spontaneous polarisation, junction potential, membrane potential, streaming potential, differential temperature cell action and lightning discharge have been given and the order of the currents due to these causes has been evaluated. The order indicates that the local earth currents due to physico-chemical causes in the earth may significantly add to the corrodibility of metals due to the physico-chemical nature of the soil. Longline telegraph cables may sometimes be damaged by corrosion due to the current induced by magnetic storms. The effect of all other geoelectric currents on the corrodibility of metals in soil is insignificant.

Response of currents in Earth’s and Saturn’s dayside magnetopause to a sudden change in the solar wind density

When the effect of a solar wind dynamic pressure pulse on the magnetospheric and ionospheric dynamics is studied, it is usually difficult to detect the effect of a sudden change in the density against the background of the other varying solar wind parameters, which often play a most pronounced role. Cases in which the solar wind plasma density gradient dominated in the dynamics of the different parameters of an interplanetary medium and its magnetic field are considered in this work. Variations in the Earth’s dayside magnetopause current caused by a change in the solar wind ion density are presented for two such cases (February 11 and January 11, 1997) based on the method developed by us previously. Variations in the dayside magnetopause current for collisions of the magnetosphere with corotating interacting flows in January 2004, studied in detail by us previously, are also presented for Saturn. The estimates are comparable with the current values in the transitional three-dimensional current systems of Saturn that were previously calculated by us.

The Mechanism of the Earth's Epidermis Warming Caused by Exploitation of Fossil Fuels

The techniques are referred to as analyzing the relationship between the events of the lithosphere getting thermal and the changes of weakened release energies of strong earthquakes that might be related with the ones of increased exploitation quantities of the global three-large fossil fuels of coal,oil and gas ,and the relationship between the events of earth crust expansion getting thermal with the accumulated increasing of the land crust expansion thickness from calculation and the accumulated increasing of fossil fuels being exploited,et al. The three mechanism-modes of earth's epidermis warming over the past 100 years since 1890 from earth interior changes with relation to fossil fuels being exploited were suggested that the weakened release energies of global strong earthquakes caused by the increasing of earth thermal stress energies and overall warming of lithosphere, the “weightlessness” and expansion and getting thermal of continental crust,the increasing of earth currents and heat quantities generated by added origid geological and tectonic activities in mining areas and earth's surface getting thermal.

Earth electricity: a review of mechanisms which cause telluric currents in the lithosphere

Telluric currents are natural electrical phenomena in the Earth or its bodies of water. The strongest electric currents are related to lightning phenomena or space weather. Earth electricity can cause damage to structures, and may be useful for earthquake forecasting and other applications. Thirty-two distinct mechanisms that cause Earth electricity are described, and a broad selection of current research is highlighted.

Monitoring geomagnetic signals of groundwater movement using multiple underground SQUID magnetometers

Groundwater can influence the geomagnetic field measured underground in at least two key ways. The water levels in rock will determine its electrical conductivity, and thus change the magnitude of the telluric currents induced in the rock by changing magnetic fields generated in the ionosphere. This can be studied by using multiple magnetometers at different underground locations. Secondly the flow of water through rock will generate a small magnetic signal, of unknown magnitude, through the electrokinetic effect. SQUID magnetometry has the potential to allow passive studies of groundwater changes in complex systems such as karst. We have monitored geomagnetic signals using two SQUID magnetometers at the LSBB underground laboratory, and set an initial limit on the magnitude of the electrokinetic signal. We now plan to carry out a longer term measurement using three SQUID systems as well as fluxgate sensors to track changes in the gradient of the magnetic field across the underground complex.

Evaluación de la resistencia del suelo en Casanare, Colombia

El presente artículo contiene los resultados obtenidos durante la interpretación de los datos de resistencia del suelo, correspondientes a los trabajos realizados en la ciudad de Monterrey, Casanare, Colombia. El objetivo principal de esta investigación, estuvo dado en encontrar el punto óptimo donde sería ubicada la toma a tierra de una subestación, que consta de un sistema electrónico o planta generadora o transmisora de radiofrecuencia. En el trabajo se presenta una descripción del método geofísico de corrientes telúricas, la metodología y los resultados obtenidos a partir de 21 puntos de mediciones, en una red regular. Se presenta el mapa de resistividades y el mapa de isolíneas del área que permitieron diferenciar las diferentes zonas.

Earthquakes and global electrical circuit

Based on recent experimental and theoretical model results, the role of earthquakes and processes of their preparation as electricity sources in the global electric circuit (GEC) is discussed. In addition to the traditional elements of the GEC, such as thunderstorm currents, ionosphere currents, fair weather currents, and telluric currents, hypothetical seismogenic currents flowing between the faults and the ionosphere are considered. The ionization sources for these currents are presumably the radiation of radioactive gases and the ionization by the electric field of so-called “positive holes” created by the compression of tectonic plates, whereas transportation of electric charges between the Earth and the ionosphere occurs under the action of electric fields and turbulent diffusion (for heavy charged species). Seismogenic currents deliver electric charges into the ionosphere, which give rise to electric fields in it and in the magnetically conjugated region. The drift of magnetized plasma in the ionosphere F2-region and plasmasphere plasma under the action of these fields causes disturbances in the electron density and total electron content (TEC) of the ionosphere, which are observed by GPS satellites before strong earthquakes. The typical features of these disturbances (magnitudes, dimensions, stability, nighttime predominance of the relative TEC disturbances, geomagnetic conjugacy) are well reproduced in theoretical model calculations based on the solution of the equation for the electric ionosphere potential with specified seismogenic electric current at the lower boundary of the ionosphere if this current is strong enough (comparable with thunderstorm currents). The feasibility of such seismogenic currents is discussed. It is argued that the TEC disturbances observed before strong earthquakes cannot be explained by neutral atmosphere disturbances. These TEC disturbances can be treated as ionospheric earthquake precursors created by seismogenic GEC disturbances.

Relationship of electric power quality to milk production of dairy herds — Field study with literature review

Public Utility Commissions (PUC) in several states adopted 0.5volt rms (root mean squared) or 1.0milliampere as the actionable limit for utilities to respond to complaints of uncontrolled voltage. This study clearly shows that the actionable level should be reduced to 10mV p-p (peak-to-peak), which is 140 times less than the current standard. Dairy farmer complaints that animal behavior and milk production were affected by electrical shocks below adopted standards were investigated on 12 farms in Wisconsin, Michigan, and Minnesota. Milk production per cow was determined from daily tank-weight pickup and number of cows milked. Number of transient events, transients, voltage p-p, waveform phase angle degree, sags, and sag-Vrms were measured from event recorders plugged into milk house wall outlets. Data from 1705 cows and 939 data points were analyzed by multiherd least-squares multiple regression and SAS-ANOVA statistical programs. In five herds for 517days, milk/cow/day decreased −0.0281kg/transient event as transient events increased from 0 to 122/day (P<0.02). Negative effects on milk/cow/day from event recorder measurements were significant for eight independent electrical variables. Step-potential voltage and frequency of earth currents were measured by oscilloscope from metal plates grouted into the floor of milking stalls. Milk decreased as number of 3rd, 5th, 7th, 21st, 28th, and 42nd harmonics and the sum of triplen harmonics (3rd, 9th, 15th, 21st, 27th, 33rd, and 39th) increased/day (P<0.003). Event recorder transient events were positively correlated with oscilloscope average V p-p event readings. Steps/min counted from videotapes of a dancing cow with no contact to metal in the barnyard were correlated with non-sinusoidal 8.1 to 14.6mV p-p impulses recorded by oscilloscope for 5min from EKG patches on legs. PUC standards and use of 500-Ohm resistors in test circuits underestimate effects of non-sinusoidal, higher frequency voltage/current common on rural power lines.