Grounding Electrode System Research Articles

Analysis of the stress-strain state of a vertical ground electrode system for permafrost soils under pushing loads

The article proposes the design, design scheme and model of a vertical ground electrode system with lobe lugs for permafrost soils. The model was implemented using the ANSYS software. In the design scheme, the soil — ground electrode system is taken into account, the elastic-plastic properties of the soil are taken into account by the Drucker — Prager model. When modeling the work of the foundation soils, the Mises strength condition was adopted, according to which the equivalent stress is calculated under the condition of the material hydrostatic compression. The following boundary conditions are accepted: a cylinder-shaped soil mass is rigidly fixed along the lower face and along the side surface of the cylinder. Calculations are made for 5 standard sizes of grounding conductors. Maps of the distribution of stresses in the metal structure of the ground electrode (the rod and petals-emphasis) are received, the movements of the ground electrode in the soil mass are determined. The dependences between the maximum equivalent stresses in the ground electrode lobes and the value of vertical displacement in the ground base are established, as well as the amount of movement of the earthing pad, at which the effective equivalent voltages reach critical values in the area where the paddles are adjacent to the rod.

Fault Location Algorithm Based on Characteristic- Harmonic Measured Impedance for HVdc Grounding Electrode Lines

It is still a significant challenge to accurately locate faults of grounding electrode lines in high-voltage direct current (HVdc) transmission systems, especially high resistance faults and remote faults. In this article, a novel fault location approach based on characteristic-harmonic measured impedance (CHMI) is proposed. This method works well under high resistance faults and remote faults. Considering that there are abundant and steady characteristic harmonics in electrical signals of grounding electrode lines, the CHMI is defined first according to the equivalent circuit of the grounding electrode system. Then, the CHMIs of the two grounding electrode lines under faults are analytically derived. On the basis of that, the fault branch is identified by the amplitude ratio of the two CHMIs. Furthermore, since both of the CHMIs of the two lines are relevant to fault distance and fault resistance, the precise fault distance is obtained by solving two fault location functions simultaneously and eliminating fault resistance. The proposed algorithm is finally validated through numerous simulations covering various fault scenarios carried out in PSCAD/EMTDC.

The Effect of Grounding Electrode Parameters on Soil Ionization and Transient Grounding Resistance Using Electromagnetic Field Approach

The soil ionization phenomenon occurs during the dispersion of lightning current into the earth. This phenomenon causes the grounding electrode resistance to be effectively reduced. The extension of the soil ionization depends on the current amplitude along the electrode and the resultant electric field intensity surrounding the electrode. The electrical and physical parameters of the grounding electrode system are found as factors that affect the electric field intensity. In this study the electromagnetic field approach and the soil breakdown theory are taken into account to investigate the effect of the mentioned factors on soil ionization and grounding resistance. Changing the parameters of the grounding electrode system affect the electric field distribution around the electrode. Based on the conditions the grounding electrode resistance was reduced between 12% to 75% by considering the soil ionization effect.

탄소혼합물 접지전극의 접지임피던스의 특성

This paper presents characteristics of frequency-dependent grounding impedance and transient grounding impedance for the carbon compound grounding electrode used in the installation of computerized electronic equipment and lightning protection system. The frequency-dependent grounding impedances were measured by applying sinusoidal currents in the frequency range from 100 [Hz] to 10[MHz], and the transient grounding impedances were examined by subjecting the impulse current with the front-time between 1~80[]. As a result, the ground resistance of the carbon compound grounding electrode is less than that of another type grounding electrodes. The transient grounding impedance is relatively low and the conventional grounding impedance is rather lower than the ground resistance. The frequency-dependent grounding impedance of the carbon compound grounding electrode is capacitive and the grounding impedance is decreased with increasing the frequency of injected currents. Therefore in the case that the carbon compound grounding electrode is jointly used with large-scaled grounding electrodes, it is possible to reduce the high frequency grounding impedance of the integrated grounding electrode system.

수조모델을 이용한 메쉬접지극의 접지저항에 관한 연구

Recently, a number of equipments related with electricity, electronics, and communication in the same building are needed to the grounding system for safety from unexpected accidents. When the faulted electric current flows into a certain grounding system, the potential rise in that system takes place and it might induce the potential rise to other grounding system. This potential interference was strongly affected by the surface potential, which was deeply related with the electrode shape. In this paper, the fundamental formula was deduced on the basis of surface potential of two grounding electrodes. Which corresponds to source of the potential interference and other grounding electrode, respectively. Therefore, the degree of potential interference in this mesh grounding electrode system was verified by the simple model simulation. In addition, in order to identify the difference between the grounding resistance in the realistic construction site and the expected value from the corresponding simulation, the experiment was performed with model on a reduced scale about the realistic grounding system. It consists of stainless steel hemisphere electrodes in a water tank. From this work, the grounding resistance in the mesh grounding electrode showed the good coincidence results between those. Consequently, it is confirmed that the grounding resistance in the mesh electrode is possible to be estimated by performing the experiment using the water tank model.

Ground Resistance Measurement With Alternative Fall-of-Potential Method

An alternative fall-of-potential method is presented to measure on-line and in situ resistance of ground electrode systems in low-voltage distribution networks. It provides simultaneous resistance measurements of both equivalent ground electrode system of a substation and ground electrode of a premise. The method does not require usage of any auxiliary electrode, but employs two existing ground electrodes in the distribution network. The method has the advantage that it uses moderately high currents than the classical fall-of-potential method, and results are independent of test electrode positions. The method is especially useful in urbanized districts where it is difficult to apply the classical fall-of-potential method. Also, a capacitive potential probe was successfully tested in place of the current electrode used in the fall-of-potential method.

Earth Ground Resistance Testing for Low-Voltage Power Systems

A quality connection to earth through the grounding electrode system for a commercial or industrial facility's power system is necessary for: 1) providing a low impedance path for lightning stroke current dissipation, 2) the reduction of "Step" and "Touch" potentials under line-to-earth fault conditions, and 3) the dissipation of electrostatic charges. Previously accepted test methods for resistance measurements of a grounding electrode system may indicate incorrectly that high or low resistance connections have been established. Testing of several grounding electrode systems was conducted by the author. This paper will present results of these tests to illustrate deficiencies in grounding electrode resistance test methods that have been accepted previously. Inaccuracies of various test instrument principles will also be discussed. The author found that close attention to the test procedure must be given to ensure that an accurate measurement will be achieved. This paper will provide recommendations on measure- ment techniques to minimize errors and ensure valid test results.

Communication Some Observations on Tree Patterns in Pmma Under Alternating Voltages

Observations of the development of electrical trees in polymethy-lmethacrylate (PMMA) using a single needle plane ground electrode system and 50 Hz voltages are reported for both voidless samples and samples having an artificial void. The temporal changes in the tree pattern from branch-like to bush- or fan-like observed in the voidless specimens are intimately associated with the occurrence of localized cracks. No change in pattern and no cracks occur in samples with an artificial void. The results support the theory that a gaseous discharge occurs in the various hollow channels of the branch-like tree pattern.