Ground Mat Research Articles

빌딩 위험전압의 접지시스템 설계 방법에 관한 연구

접지저항값은 안전범위 안에 있는 인체 허용 접촉전압(ESUBtouch/SUB)값 이하가 되도록 설계 하여야 하며, 인체를 투과하는 전류가 달라 보폭전압(ESUBstep/SUB) 한계가 접촉전압(ESUBtouch/SUB) 한계 보다 커서 인체 허용 접촉전압(ESUBtouch/SUB)값 이하가 되면, 보폭전압(ESUBstep/SUB) 요건도 만족한 것으로 볼 수 있다. 본 논문의 취지는 한국전기안전공사 공사계획신고 설계도서(접지 계산서 및 설계도면)의 공사시 제출목록인 접지 계산서의 빌딩 접지저항값을 1 Ω이하, 접지 프로그램 SKM Power tools ground mat 으로 허용 접촉전압(ESUBtouch/SUB) 551.62V, 허용 보폭전압(ESUBstep/SUB)1714.32V 이하로 설계조건을 완성한다. 조건 값을 Mseh간격 5X5 m에 접지봉 4개를 매설깊이 0.8 m로 적용하여 예상 접촉전압(ESUBt/SUB) 93V, 예상 보폭전압(ESUBs/SUB) 428.6V 접지저항값은 0.26 Ω이 되었고, Mseh 간격 10X10 m에 접지봉 8개를 매설깊이 0.5 m로 변화시켜 예상 접촉전압(ESUBt/SUB) 111V, 접지저항은 0.28 Ω으로 도출되어, 요구되는 ESUBtouch/SUB>˃ESUBt/SUB, ESUBstep/SUBESUBs/SUB로 빌딩 접지저항값 1 Ω이하 안전전압으로 설계된 것을 확인할 수 있었다.

Relation Of Some Biochinamatic Changes With The Level Of Conducting Artistic Skills On The Ground Mat Movements Of The Junior Gymnasts In Erbil

Relation Of Some Biochinamatic Changes With The Level Of Conducting Artistic Skills On The Ground Mat Movements Of The Junior Gymnasts In Erbil

Effect of Compelled Body Weight Shift (CBWS) Therapy in Comparison to ProprioceptiveTraining on Functional Balance, Gait, andMuscle Strength Among Acute Stroke Subjects.

Background:The majority of poststroke individuals tend to exhibit reduced loading over the paretic lower extremity, leading to increased postural sway, and gait asymmetry predisposing to a higher number of falls. Compelled body weight shift (CBWS) therapy is an innovative method aimed to force body weight shift toward the paretic extremity. Proprioceptive training (PT) is another method that improves balance ability contributing to the increase in muscle activity. Both the CBWS and PT have been shown to improve the quality of life in stroke subjects.Purpose:The aim of this study is to compare the effects of CBWS therapy and PT in improving balance, kinematic gait parameters, and muscle strength among acute stroke patients.Methods:Thirty subjects were nonrandomly divided into two groups where both groups received routine physiotherapy for two weeks in addition to which the CBWS group incorporated a 15 mm platform placed under the unaffected extremity while the PT group included incorporated proprioceptive exercises on the ground and foam mat. Functional balance, functional mobility, videographic analysis of degrees of hip flexion, knee hyperextension, and ankle dorsiflexion along with gait speed and satiotemporal gait parameters were obtained.Results:The pre-post analysis within both groups revealed statistically significant improvement in all parameters except for the kinematic parameters of gait. However, no statistically significant difference was observed between the CBWS and PT groups.Conclusion:CBWS can be used as an alternative to PT in the rehabilitation of stroke patients concerning balance and gait. CBWS provided during active treatment sessions results as effective as those seen as a result of all-day therapy.

The Flexibility in Terms of Some Biomechanical Indicators and their Relationship to the Performance of the Skill of the Hands Jump Back on the Ground Mat

The biomechanics of Gymnastics sport in general is the flexible in particular, the game of gymnastics has witnessed a rapid and significant development during the past decade and became involved in the game counted on a lot in the Olympic decorations being one of the multiple individual games with different activities, which can get multiple medals in the event that the team A high level of technical performance as medals that are calculated differentially to the participating countries as well as because they are games that need integrated qualities and overlapping and complex to reach high technical performance, and given the development of sport and its association with other sciences, including biomechanics The research aims to identify the elasticity of some bomechanical indicators and their relationship with the hands jump back of the cubs players in the artistic gymnastics, whereas the research methodology used the descriptive approach in the way of correlation relationships, and the research community included the cubs players in the artistic club Al-Kout sports (6) players, and (2) players who were surveyed were excluded.

The Effect of Teaching with Mobile Learning Technology on Learning the Artistic Performance and Improving the Most Important Bio-Kinematic Variables for Rear Rolling for Standing on Hands on the Ground Mat

The Effect of Teaching with Mobile Learning Technology on Learning the Artistic Performance and Improving the Most Important Bio-Kinematic Variables for Rear Rolling for Standing on Hands on the Ground Mat

Dynamic motion mat design to improve the performance of kinetic sentences on ground mat in gymnastics

Dynamic motion mat design to improve the performance of kinetic sentences on ground mat in gymnastics

Computational Modelling of a Novel Three Dimensional Ground Mat for 33/11kV Central Switching Station

Computational Modelling of a Novel Three Dimensional Ground Mat for 33/11kV Central Switching Station

Electro-Magnetic-Acoustic Transducers for Automatic Monitoring and Health Assessment of Transmission Lines

This paper presents analysis, design, development, and experimental verification of a non-destructive monitoring system for diagnosis of mechanical integrity of electric conductors based on the concept of Electro-Magnetic-Acoustic Transducers (EMAT). Electric conductors, in general, are exposed to harsh environments. Such conductors include electric transmission lines, anchor rods, and ground mat risers. For automatic failure detection and assessment of mechanical integrity of these conductors, in addition to an effective transducer, feature extraction and pattern recognition techniques have to be employed. Details of the sensor design, neural-based signature analysis, feature extraction, and experimental results of fault detection techniques are presented.

Short-circuit, coordination, and harmonic studies

The most common system studies done on power systems include: load flow, short-circuit, stability, motor starting, harmonic analysis, switching transient, reliability, cable-ampacity, ground mat and protection coordination studies. The three studies addressed in this article are short-circuit, coordination, and harmonic studies.

Control of the Distribution of Giant Rosette Species of Puya (Bromeliaceae) in the Ecuadorian Paramos

This study examined the effects of vegetation cover, growth form, fire disturbance, and competition on the distributional limits of two species of Puya in the Ecuadorian paramos. Puya clava-herculis and Puya hamata are widely distributed giant rosette plants that occupy nonoverlapping elevational ranges (3700-4100 m and 3300-3700 m, respectively) and each shows a patchy local distribution. Under natural conditions, the lower elevational limits of P. clava-herculis is primarily determined by competition with shrubs. In areas near human habitation, the lower limit of P. clavaherculis and P. hamata is largely determined by constant burning. Above the distribution of P. clava-herculis, bare ground or cushion and mat plants predominate. On bare ground, solifluction, low temperatures, and moisture stress reduce the probability of Puya establishment. In areas dominated by cushion and mat plants, either species of Puya is outcompeted or seedling safe sites are absent. Seedlings of P. clava-herculis showed a stronger than expected association with grass tussocks, indicating the importance of tussock edges as seedling safe sites. The amount and type of ground cover, as well as the distance to and growth form of nearest neighbors, are important factors determining the local patchy distribution of P. clavaherculis.

Measurement of ground potential difference at power substations

A method of obtaining a record of ground potential difference (GPD) values in substations where a remote ground and an oscillograph are available is presented. Typical recorded values of GPD range from under 100 V to a maximum of 450 V RMS. These measurements suggest that the values used for ground mat design should be considered by the telephone company engineer as conservative and that additional amounts conservatism are not necessary. The telephone company engineer should determine how the power company has calculated the requested data so that a proper judgment can be made. A history of recorded GPD values will aid in determining needed protection. Significant savings may be realized by avoiding excessive conservatism. Since the theoretical calculation of GPD results in a typical large value of voltage, the associated zone of influence will be large. Within that zone, all telephone grounds will be removed, causing greater lightning damage to the outside telephone plant. Therefore, the probability of lightning damage as compared with the likelihood of GPD-caused damage must be considered.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Ground grid design of a transition station system-a typical example of fault transfer

E.T.D. Barra Funda I urban station, located in Sao Paulo, Brazil, is surrounded by several buildings, so it is not possible to make reliable earth resistivity and ground electrode resistance measurements. The grounding of this station was designed by using external circuits connected to the ground mat (sheaths and bare copper bondings). The use of these circuits allows a transfer of the fault potentials from E.T.D. Barra Funda I to E.T.R. Barra Funda II due to a strong cable shielding. A discussion is presented of the basic procedures adopted for controlling the potential rise at the E.T.D. Barra Funda I station in order to ensure the safety of people and equipment during the occurrence of a fault to the ground. This study deals with such design aspects as: high short-circuit level, high soil resistivity and backup protection time, and reduced area for diffusion of short-circuit current. >

Grounding measurements at the Itaipu generating complex using the 'extended Eleck method'

Measurements carried out on the interconnected grounding systems of the three main substations of Brazil's Itaipu generating complex are described. These include ground mat resistances, ground impedances seen from each substation, ground potential rise, and mesh potential. The small magnitude of these ground system parameters as well as the interconnection between several nearby ground mats through the ground-wires of the 500 kV and 220 kV lines suggested the utilization of the measurement procedures introduced by A. Eleck (1962), modified for use with aluminium-cable steel-reinforced (ACSR) ground wires. The measured values showed good agreement with previously computed values. The procedures can be used to carry out grounding measurements at a single substation or to carry out simultaneous grounding measurements at two or more nearby substations, as reported here. It is shown that drastic reduction of the mat current and ground potentials is obtained by the utilization of ACSR ground-wires on some line spans near the substations, allowing the utilization of a ground mat conductor spacing several times bigger than if steel ground-wires had been used.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Transient Analysis of Grounding Systems

This paper addresses the problem of computing the ground potential rise of grounding systems during transients. Finite element analysis is employed to model the constituent parts of a grounding system. Short lengths of earth embedded electrodes are characterized as transmission lines with distributed inductance, capacitance and leakage resistance to earth. Leakage resistance to earth is accurately computed with the method of moments. The other parameters of the finite element, namely inductance and capacitance, are computed from the resistance utilizing Maxwell's equations. This modeling enables the computation of the transient response of substation grounding systems to fast or slow waves striking the substation. The result is obtained in terms of a convolution of the step response of the system and the striking wave. In this way the impedance of substation systems to 60 cycles is accurately computed. Results demonstrate the dependence of the 60 cycle impedance on system parameters. The methodology allows to interface this model of a substation ground mat with the Electromagnetic Transient Analysis Program thus, allowing explicit representation of earth effects in electromagmatic transients computations.

A Closer Look at ``the Facts of Life'' in Ground Mat Design

Rigorous analytical methods making use of the digital computer permit accurate modeling and evaluation of ground mat designs. Through imaginative use of these methods, the design of a ground mat system can be refined to the point where the need for costly and unnecessary conservatism can be eliminated. This paper demonstrates how improved design precision is possible with a ground mat study based on calculations performed by any of several computer programs that have been recently developed. An approach is examined for applying the output results from one such computer program in order to realize an optimum ground mat design. Finally, a summary is provided of the input information required to permit a ground mat system computer study. The material presented is a preliminary version of information to be included as a chapter in a new IEEE publication # 399 (the ``Brown'' book) being prepared under the sponsorship of the Industrial Power Systems Department (Power Systems Analysis sub-committee, Power Systems Support Committee) of the Industry Applications Society.

Shunt Capacitor Switching EMI Voltages, Their Reduction in Bonneville Power Administration Substations

Back to back switching of grounded Wye shunt capacitors cause high frequency, high magnitude current flow in overhead bus and ground mat conductors. Measurements of induced voltages on control cables and receptacles, transverse voltages on fuse blown PT secondaries and personnel intercept voltages are reported. BPA methods of confining transients to capacitor areas and shielding techniques are reviewed.

Instrumentation Techniques in High Voltage Substations - Part II Measuring Devices and Circuits

Resistance dividers, capacitance dividers, shunts, termination resistors, and multi-coupling devices have been developed to use with triaxial cable during EMI, LVI, and transient potential measurements. Arcing disconnects switches - back-to-back switching of shunt capacitor produce EMI voltages, intercept potential on fences and ground mat potential rise. Circuits used to measure these voltages and a method to measure ground mat surge impedance is summarized in this report.

Statistical Study of Electric Fields from Earth-Return Tests in the Western States Compared with Natural Electric Fields

Preliminary grounding tests have been carried out by the Bonneville Power Administration and by the Bureau of Reclamation in three regions of the western states, in preparation for the installation of a HVDC transmission system linking the Pacific Northwest and Southwest regions. Electric fields observed about ground mat locations in the Washington-Oregon area, the southern Nevada area, and the central California area were analyzed statistically as a function of distance from the ground mat. These fields are compared with the probable levels of natural fields induced by slow variations in the earth's magnetic field-in order to estimate the possible hazards involved in using ground return for current in a HVDC system.

Investigations-of Ground Currents and Potentials Near EHV DC Installations

Two test circuits utilizing alternating current transmission lines for conduction of direct current between electrodes are described. The earth was used as the return path. Both circuits were from the Hoover Powerplant area, one southwest toward Baker and the other south toward Needles, Calif. Potential gradients near the proposed site of the Mead terminal of the Pacific Northwest-Pacific Southwest Intertie are discussed at length. Neutral currents in numerous transformer banks, both transient and steady state are reported. Oscillograms are included which show the effect of separation of dc electrode and ac ground mat. Some data are included from similar earlier tests and comparisons made as to ground resistivity, potential gradients, etc. Test currents were on the order of 400-500 amperes with occasional values in the 600 ampere range.

Investigations of Ground Current Phenomena Associated with HV DC Transmission

A brief outline is presented of major considerations when the earth is proposed for use as a return conductor on high-voltage direct-current transmission systems. Approximate values are given of earth potential gradients near an electrode, as determined in 1963 near Tracy switchyard by relatively low magnitude test currents and small spacings of test electrodes. Similar, more precise values are listed from large-scale tests conducted in March 1964 between Tracy switchyard and a point west of Red Bluff, Calif., with larger current flows and an electrode spacing of approximately 175 miles. Disturbances of a significant level are indicated as being confined to very small areas surrounding each electrode. Details of test equipment, transmission line facilities, permanent and temporary ground mats which were used as electrodes, and locations of various oil, gas, and water lines in close proximity to the electrodes are discussed. Design, installation, and general operation of a deep well electrode adjacent to the Tracy switchyard ground mat is described. The shielding effects of separation of ac and dc grounding points, as illustrated by specific test data and confirmed in laboratory experiments, is presented. Some possibilities for use of such shielding in limiting adverse flow of direct current in the neutral circuits of high-voltage ac systems are indicated. Additional tests to obtain further data for use in final designs are suggested.