Earth Mat Research Articles

Comparative study of tyre ash and palm kernel oil cake as back-filling agents for effective grounding

A simple method for analyzing electrical earthing system is presented. The idea behind this research is to furnish the general public particularly in Ghana to understand the effectiveness of using low resistive materials to provide low resistance values for their earthing frameworks to protect lives and guarantee hardware security. Right now, proficiency of materials accessible for free, to be specific, Palm Kernel Oil Cake (PKOC) and Tyre ash, as conductive inlay material for decreasing earth terminal resistance was assessed. Earth mat 20-cm length and 10cm breath were covered with each refilling material with their exhibition contrasted with reference to the earth mat additionally covered at a similar location with raw sand, specifically, sandy gravel at a specific area in Ghana. The outcomes show that tyre ash gives a steady earth resistance in both dry and wet climate conditions and improves it significantly as compared to PKOC. The main purpose of evaluating these two local materials as a backfilling agent is to reduce the earth resistivity which in this study was achieved successfully after 3 months of monitoring.

Development of an improved earthing method for power and distribution transformers substations

Engineers and planners have realized that equipment grounding is a necessary part of installation process in Electrical power substations. Over years, grounding or earthing has been carried out primarily through preparation of Earth Mat which is interconnected with several Earth-rods buried around the equipment under consideration. This approach takes several efforts to have an acceptable and reliable result. However, this paper presents a more flexible, economical and results oriented approach. A flow chart which describes the procedures of carrying out the proposed method of earthing is developed. This was applied to two case studies: a proposed Power transformer substation and distribution Transformer substation located within the same geographical domain. On the two cases, the measured earth resistances are presented and discussed. The results from the case study indicates that the earth resistance values obtained from this new approach are reliable and in compliance with IEEE Standards 80,142, 81 and 1100. Keywords : Equipment, Grounding, Earthing, Earth-rod, Flowchart, Earth Mat, Flow Process, Injection Substation, Distribution Substation, Earth Resistance, IEEE Standard.

Earth Mat Design for 132/33Kv Substation in Rivers State Using ETAP

Earthing is an important aspect of every substation construction. Earth Mat is preferable to large substations because of space saving on the ground level due to substantial reduction of earth pits which leads to ease of coordination. Earth Mat minimizes the danger of high step or touch voltages in critical operating areas or places that are frequently used by people. Thus properly designed earthing system capable of dissipating large currents safely to earth is required, regardless of the fault type. This paper presents the design of earthing systems for the 132/33Kv substation in Rivers state of Nigeria and the review of substation practices with special reference to safety and development criteria for safe design. A real time case study has been considered and the design was done using ETAP (Electrical Transients Analyzer Program). Simulation using ETAP eradicates the error that is inherent in manual operational method that is mostly used in various substations.

The Ethical Values of <em>Narodnoe Pravoslavie</em>: Traditional Near-Death Experiences and Fedotov

In 1935 the emigre scholar G. P. Fedotov published an analysis of the ethical values of popular Russian Orthodoxy, basing his conclusions on the genre of dukhovnye stikhi (lit. spiritual verses). These religious songs were performed before the Revolution by the blind itinerant singers known as the kaleki or kaliki perekhozhie [Fedotov 1935/1991].(2) For Fedotov the key features of folk Orthodoxy (narodnoe pravoslavie) were the emphasis on life as suffering, the profound sinfulness of man, the belief in the power of Christian love and the attachment to Mother Earth (Mat’ syra zemlia) and maternal values in general, with their supreme embodiment in the Mother of God. His view has proved highly influential outside Russia, largely through its distillation in the opening chapter of volume one of The Russian Religious Mind [Fedotov 1946]. Fedotov’s influence has perhaps been reinforced by the coincidences between his own concept of folk Orthodoxy and key aspects of Dostoevskii’s view of the people (narod), itself based to a considerable extent on the writer’s reading of the dukhovnye stikhi [Ivanits 2002; Wigzell 2002b:28-31].(3) In Russia where Fedotov’s work began to appear only in 1989, his views have had less impact, while, among folklorists, there is a new interest in and awareness of the complexities of folk ethics [Belova 2002]. In this essay I question the validity of Fedotov’s analysis for popular Orthodoxy as a whole by examinng another of the genres of religious folklore, the type of vision known as the obmiranie. So unfamiliar is the obmiranie, except to some folklorists and traditional Orthodox believers, that a definition would seem in order. The term obmirat’, self-evidently linked to umirat’ (to die), refers both to the state of falling into/being in a coma as well as to the narrative account of what is seen during a coma, that is, essentially a near-death experience. To this day among traditional believers (official Orthodox or Old Believers) in rural Russia as in other Orthodox Slavic countries, the near-death experience is generally believed to consist of a journey to the world beyond the grave.(4) Here the subject most commonly meets relatives, sees the torments of hell and learns the date of his or her own death. Obviously these narratives represent a continuation of early and medieval Christian tradition (Dante’s Divine Comedy is the supreme literary example.) Visits to the world beyond the grave were traditionally experienced not only during coma but also as dreams, or, when awake, as visions, but in Orthodox Slavic countries in the nineteenth and twentieth centuries such visions are linked primarily with a coma or unusually prolonged and deep sleep. Indeed, it is traditionally assumed that anyone in this state will visit the afterlife, and in particular hell. During the vision, even when heaven is mentioned, the specific virtues of the blessed are not. Consequently, the ethical emphases of the obmiranie have to be judged largely from the sins mentioned, whether those of categories of sinners, or specific people known to the visionary, including his or her own moral failings. Within the Byzantino-Slavic Orthodox tradition considerable differences exist between accounts of visits to heaven and hell, allowing the visionary to select

A Separate Earthing Network for I & C Cables and Equipment in the Context of Signal Integrity and EMI in a Power Station

Instrumentation & control signals are subject to increasing levels of EMI as unit sizes increase. The paper is about an earthing network separately laid for I & C equipment and cables to obtain improved signal integrity. The network is terminated at the station earth mat to which the conventional earthing network associated with power equipment is also connected. The functions & utility of such a separate earthing network are discussed.

Possible errors of a particular wide-aperture direction-finder

A study is made of the extent to which the high-frequency cyclical direction-finder devised by Earp and Godfrey is subject to three common types of error. First, the result is presented of theoretical computations on the errors given by a practical fixed-aerial system in wave-interference conditions. The variance of these errors as the phase difference between the incident rays is varied is shown to be the same as that given by the ideal rotating-aerial version of this direction-finder; it is appreciably smaller than that of an Adcock for a system aperture of 4λ, and, in general, much smaller for an aperture of 10λ. Secondly, errors due to aerial interaction are considered for a system of 24 unipoles, 9m high and 1.1 m in diameter, placed on a circle of 100m diameter. It is concluded that the errors in indicated bearing are likely to be negligible, provided that the aerials not in use at any instant are terminated by a resistor equal to their nominal characteristic impedance. Finally, the polarization error is examined for such a system in which surface feeders are used, without an earth mat, on ground of moderate conductivity; it is found to be small, being greatest at the low-frequency end of the band, where the standard-wave error is about 1° at 3 Mc/s. With extended feeders the errors at low frequencies are reduced considerably.

The use of earth mats to reduce the polarization error of U-type Adcock direction-finders

The paper deals with the experiments carried out in 1943–44 to investigate the use of an earth screen or mat to reduce the polarization errors of the U-type Adcock direction-finder. These errors arise from the introduction of signal voltages into the system by the horizontally polarized component of the incident waves, when the aerial feeders are laid on, or buried in, ground of poor conductivity. The polarization error of a standard form of direction-finder, erected in the normal manner on highly conductive ground (3 × 108 e.s.u., or about 3 × 103 ohm-cm resistivity) at the Radio Research Station, Slough, was measured over the frequency range 3–10 Mc/s, with the aid of a local transmitter which radiated at controllable angles of incidence and polarization. An earth mat, about 31 m in diameter and of a square mesh between 0.3 and 1 m, was then installed at the direction-finder, and the measurements were repeated for various experimental arrangements of this installation.When the mat was raised above and insulated from the ground, the polarization error of the direction-finder was seriously increased; but when the mat was effectively earthed (both around its perimeter and at an intermediate radius) the error was slightly reduced. In place of the direct earth connection, a similar result was achieved by attaching radial wires to the perimeter of the mat, the length of the wires being selected to resonate at the frequency in use. By using a combination of 108 wires of 11, 15 and 25 m lengths, arranged so that there were 36 of each length, the desired reduction in the polarization error was attained more or less uniformly over the whole of the 3–10 Mc/s range.Additional experiments were carried out at Martlesham on ground of such poor conductivity (107 e.s.u., or about 105 ohm-cm resistivity), that direct earth connection to the mat was ineffective. The results confirmed the previous deduction that the attachment of radial wires of suitable length and disposition makes the earth mat effective. It was also shown that both mat and radial extension wires may be laid on the ground if desired. Furthermore, it was shown that, with the mat in position, it was no longer necessary to bury the aerial feeders, but was sufficient to lay the feeders on the ground just under the mat, or along the surface of the mat, if the feeder screen was well bonded to the mat. An additional advantage of the use of such an arrangement is that it smooths out the effects of any irregularities in the ground at the site, and produces a corresponding improvement in the performance of the direction-finder.Comparison of observations made at the same site with two direction-finders, one equipped with an earth mat and one without, showed that when taking bearings on signals from stations at distances ranging from 200 km to nearly 800 km, the expected appreciable improvement in overall performance due to the mat was attained.

A simple method of reducing the polarization error of a U-type Adcock direction-finder

A brief description of the nature of polarization error, and the historical background of earlier work and measuring techniques, introduces the instrumental problems associated with improving the performances of U-type Adcock direction-finders, particularly on sites of poor conductivity.An Army transportable U-type Adcock direction-finder, having surface feeders and an earthing system designed for speedy installation, was tested on a site of good conductivity, and compared well with similar but more elaborate systems, indicating a standard-wave error of only a few degrees. A series of tests on ground of abnormally low conductivity, over the frequency range 2–10 Mc/s, showed that a simple counterpoise of eight radial elements could have an effectiveness comparable with that of elaborate earthing arrangements of a more permanent nature.Quantitative comparisons of the effects of various earthing arrangements (buried feeders and extended earthing plates associated with Marconi direction-finders Types DFG24/2 and DFG25) are necessarily restricted to the small frequency range 2–5 Mc/s, on account of limitations which prevent the local source from simulating plane (or natural) wave conditions and also to enable a simple workable analysis, applicable only to electrically small systems, to be used. However, this lower region of the high-frequency band is a part where reduction of polarization error is particularly required.The computed performance of a simple unscreened U-Adcock direction-finder reveals that adding a feeder screen without adequate earth return at its ends, can have a deleterious effect, but with care a fair improvement over a closed loop (reduction in standard-wave error from 35 deg to 20 deg) can be achieved on an exceptionally poor site. On a good site the performance of a U-Adcock direction-finder, even without feeder screens, is far superior to a loop. Tests on an average type of unfavourable site to be found in this country, show that the use of an eight-radial counterpoise, which, on average reduces polarization error by 4 to 1, results in a performance comparable with that for a very good site.Data available from polarization-error measurements on a directionfinder with a large circular earth mat refer only to limited measuring conditions and do not allow a strict comparison, but from general considerations a greater efficacy in reducing polarization error as compared with an 8-wire radial system can be expected. The present tests, though limited, reveal fundamental points which would suggest that a layer of crushed coke might confer similar benefits to an earth mat.The simplicity of the counterpoise of eight long radials is such, however, that its use is suggested for all but the best sites, so as to make performance less dependent on weather, and because it facilitates the approach of an external cable with a minimum of disturbance. Even with the suggested coke layer its use should still be beneficial.