Residential Commercial And Industrial Electrical Systems Equipment And Selection Pdf
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Residential, Commercial and Industrial Electrical Systems is a comprehensive coverage on every aspect of design, installation, testing and commissioning of electrical systems for residential, commercial and industrial buildings. This book would serve as a ready reference for electrical engineers as well as bridge the gap between theory and practice, for students and academicians, alike. This book elaborately presents advanced topics like harmonics and interference, various testing procedures and practices necessary to avoid premature failure of electrical equipment.
- Residential, Commercial and Industrial Electrical Systems : Equipment and Selection
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- Residential Commercial & Industrial Electrical Systems Vol 1 Equipment & Selection
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Residential, Commercial and Industrial Electrical Systems : Equipment and Selection
An earthing system UK and IEC or grounding system US connects specific parts of an electric power system with the ground , typically the Earth's conductive surface, for safety and functional purposes. Regulations for earthing systems vary considerably among countries, though most follow the recommendations of the International Electrotechnical Commission. Regulations may identify special cases for earthing in mines, in patient care areas, or in hazardous areas of industrial plants.
In addition to electric power systems, other systems may require grounding for safety or function. Tall structures may have lightning rods as part of a system to protect them from lightning strikes. Telegraph lines may use the Earth as one conductor of a circuit, saving the cost of installation of a return wire over a long circuit. Radio antennas may require particular grounding for operation, as well as to control static electricity and provide lightning protection.
A primary component of earthing systems is static dissipation system grounding , whether it be lightning-induced or friction-induced like wind blowing against an antenna mast.
System grounding works by sending any built up static discharge to the ground through a heavy grounding electrode conductor and then into an earthing electrode. System Grounding is not to be confused with Equipment Grounding. Equipment grounding is a component of electrical systems that protects against fault currents. Fault currents are mainly caused by insulation failure of a conductor and subsequent contact with a conductive surface.
This type of grounding is not a grounding connection, technically speaking. It is a low-impedance bonding connection between the neutral and ground bus-bars in the main service panel and nowhere else.
The over-current protective devices sense this as a short-circuit condition and open the circuit, safely clearing the fault. Equipment grounding standards are set by the National Electric Code. A functional earth connection serves a purpose other than electrical safety, and may carry current as part of normal operation. Other examples of devices that use functional earth connections include surge suppressors and electromagnetic interference filters.
In low-voltage networks , which distribute the electric power to the widest class of end users, the main concern for design of earthing systems is safety of consumers who use the electric appliances and their protection against electric shocks.
In the developing world, local wiring practice may or may not provide a connection to an earth. For a time, US National Electrical Code allowed certain major appliances permanently connected to the supply to use the supply neutral wire as the equipment enclosure connection to ground.
This was not permitted for plug-in equipment as the neutral and energized conductor could easily be accidentally exchanged, creating a severe hazard. If the neutral was interrupted, the equipment enclosure would no longer be connected to ground. Normal imbalances in a split phase distribution system could create objectionable neutral to ground voltages. Recent editions of the NEC no longer permit this practice.
For similar reasons, most countries have now mandated dedicated protective earth connections in consumer wiring that are now almost universal. In the distribution networks, where connections are fewer and less vulnerable, many countries allow the earth and neutral to share a conductor. If the fault path between accidentally energized objects and the supply connection has low impedance, the fault current will be so large that the circuit overcurrent protection device fuse or circuit breaker will open to clear the ground fault.
Where the earthing system does not provide a low-impedance metallic conductor between equipment enclosures and supply return such as in a TT separately earthed system , fault currents are smaller, and will not necessarily operate the overcurrent protection device.
In such case a residual-current device is installed to detect the current leaking to ground and interrupt the circuit. The first letter indicates the connection between earth and the power-supply equipment generator or transformer :. The second letter indicates the connection between earth or network and the electrical device being supplied:. In a TN earthing system, one of the points in the generator or transformer is connected with earth, usually the star point in a three-phase system. The body of the electrical device is connected with earth via this earth connection at the transformer.
This arrangement is a current standard for residential and industrial electric systems particularly in Europe. The conductor that connects the exposed metallic parts of the consumer's electrical installation is called protective earth PE ; see also: Ground.
The conductor that connects to the star point in a three-phase system, or that carries the return current in a single-phase system, is called neutral N. Three variants of TN systems are distinguished:. For example, the sheaths on some underground cables corrode and stop providing good earth connections, and so homes where high resistance "bad earths" are found may be converted to TN-C-S.
This is only possible on a network when the neutral is suitably robust against failure, and conversion is not always possible. The PEN must be suitably reinforced against failure, as an open circuit PEN can impress full phase voltage on any exposed metal connected to the system earth downstream of the break.
The alternative is to provide a local earth and convert to TT. The main attraction of a TN network is the low impedance earth path allows easy automatic disconnection ADS on a high current circuit in the case of a line-to-PE short circuit as the same breaker or fuse will operate for either L-N or L-PE faults, and an RCD is not needed to detect earth faults.
In a TT French: terre-terre earthing system, the protective earth connection for the consumer is provided by a local earth electrode, sometimes referred to as the Terra-Firma connection and there is another independently installed at the generator. There is no 'earth wire' between the two. The big advantage of the TT earthing system is the reduced conducted interference from other users' connected equipment.
TT has always been preferable for special applications like telecommunication sites that benefit from the interference-free earthing. Also, TT networks do not pose any serious risks in the case of a broken neutral. In addition, in locations where power is distributed overhead, earth conductors are not at risk of becoming live should any overhead distribution conductor be fractured by, say, a fallen tree or branch.
But as residual current devices mitigate this disadvantage, the TT earthing system has become much more attractive providing that all AC power circuits are RCD-protected. In some countries such as the UK TT is recommended for situations where a low impedance equipotential zone is impractical to maintain by bonding, where there is significant outdoor wiring, such as supplies to mobile homes and some agricultural settings, or where a high fault current could pose other dangers, such as at fuel depots or marinas.
This can impose added requirements on variable frequency drives and switched-mode power supplies which often have substantial filters passing high frequency noise to the ground conductor. While the national wiring regulations for buildings of many countries follow the IEC terminology, in North America United States and Canada , the term "equipment grounding conductor" refers to equipment grounds and ground wires on branch circuits, and "grounding electrode conductor" is used for conductors bonding an earth ground rod or similar to a service panel.
The neutral is grounded earthed at each consumer service point thereby effectively bringing the neutral potential difference to zero along the whole length of LV lines. In the UK and some Commonwealth countries, the term "PNE", meaning Phase-Neutral-Earth is used to indicate that three or more for non-single-phase connections conductors are used, i. A resistance earth system is used for mining in India as per Central Electricity Authority Regulations.
Due to the fault current restriction it is safer for gassy mines. By comparison, in a solidly earthed system, earth fault current can be as much as the available short-circuit current.
The neutral earthing resistor is monitored to detect an interrupted ground connection and to shut off power if a fault is detected. To avoid accidental shock, current sensing circuits are used at the source to isolate the power when leakage current exceed a certain limit.
Previously, an earth leakage circuit breaker is used. In industrial applications, earth leakage relays are used with separate core balanced current transformers. This is used in the trailing cables of mining machinery. This type of circuit is a must for portable heavy electric equipment like LHD Load, Haul, Dump machine being used in under ground mines.
In high-voltage networks above 1 kV , which are far less accessible to the general public, the focus of earthing system design is less on safety and more on reliability of supply, reliability of protection, and impact on the equipment in presence of a short circuit. Only the magnitude of phase-to-ground short circuits, which are the most common, is significantly affected with the choice of earthing system, as the current path is mostly closed through the earth. There are five types of neutral earthing: .
In solid or directly earthed neutral, transformer's star point is directly connected to the ground. In this solution, a low-impedance path is provided for the ground fault current to close and, as result, their magnitudes are comparable with three-phase fault currents.
To limit short circuit earth fault an additional neutral earthing resistor NER is added between the neutral of transformer's star point and earth. With low resistance fault current limit is relatively high. High resistance grounding system grounds the neutral through a resistance which limits the ground fault current to a value equal to or slightly greater than the capacitive charging current of that system.
In unearthed , isolated or floating neutral system, as in the IT system, there is no direct connection of the star point or any other point in the network and the ground. As a result, ground fault currents have no path to be closed and thus have negligible magnitudes. However, in practice, the fault current will not be equal to zero: conductors in the circuit — particularly underground cables — have an inherent capacitance towards the earth, which provides a path of relatively high impedance.
Systems with isolated neutral may continue operation and provide uninterrupted supply even in presence of a ground fault. In urban distribution networks with multiple underground feeders, the capacitive current may reach several tens of amperes, posing significant risk for the equipment. The benefit of low fault current and continued system operation thereafter is offset by inherent drawback that the fault location is hard to detect. According to the IEEE standards, grounding rods are made from material such as copper and steel.
For choosing a grounding rod there are several selection criteria such as: corrosion resistance, diameter depending of the fault current , conductivity and others. In recent decades, there has been developed chemical grounding rods for low impedance ground containing natural electrolytic salts. Connectors for earthing installation are a means of communication between the various components of the earthing and lightning protection installations earthing rods, earthing conductors, current leads, busbars, etc.
For high voltage installations, exothermic welding is used for underground connections. Its resistance depends on the efficiency of the removal of unwanted currents to zero potential ground. The resistance of a geological material depends on several components: the presence of metal ores, the temperature of the geological layer, the presence of archeological or structural features, the presence of dissolved salts, and contaminants, porosity and permeability.
There are several basic methods for measuring soil resistance. The measurement is performed with two, three or four electrodes. The measurement methods are: pole-pole, dipole-dipole, pole-dipole, Wenner method, and the Schlumberger method.
From Wikipedia, the free encyclopedia. Physical equipment that provides a low-impedance connection between a circuit or electrical installation and earth ground. This article is about electrical supply earthing systems. This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed.
TN-S : separate protective earth PE and neutral N conductors from transformer to consuming device, which are not connected together at any point after the building distribution point. The TT French: terre-terre earthing system. This section needs expansion. You can help by adding to it. October
An earthing system UK and IEC or grounding system US connects specific parts of an electric power system with the ground , typically the Earth's conductive surface, for safety and functional purposes. Regulations for earthing systems vary considerably among countries, though most follow the recommendations of the International Electrotechnical Commission. Regulations may identify special cases for earthing in mines, in patient care areas, or in hazardous areas of industrial plants. In addition to electric power systems, other systems may require grounding for safety or function. Tall structures may have lightning rods as part of a system to protect them from lightning strikes. Telegraph lines may use the Earth as one conductor of a circuit, saving the cost of installation of a return wire over a long circuit.
Thisbookwouldserveasareadyreferencefor electricalengineers as well as bridge the gap between theory and practice, for students and academicians,alike. Volume1: Equipment andSelectionprovidesitsreadersadetaileddescriptionof variousequipmenttypicallyusedinelectrical distributionsystem. The second edition of this popular engineering reference book, previouslyentitled the Newnes Electrical Engineer's Handbook, aims to provide a basic understanding of the. Standard application of electrical details , Jerome F. The Practical electrical reference book a compact summary of information for electrical engineersand students, Erhard Jacobi, , Electric engineering, pages. Offshore electrical engineering , Geoff T. Part A, Design considerations, provides guidance for allworks on the fixedwiring and integral electrical equipment used for electrical services within healthcare premises.
Table of Contents 2. Dedication 3. Preface 4. Acknowledgements 5. Project Procedures 7. Regulations and Standards 8. Power Company Network 9.
Residential Commercial & Industrial Electrical Systems Vol 1 Equipment & Selection
Homes typically have several kinds of home wiring, including Electrical wiring for lighting and power distribution, permanently installed and portable appliances, telephone, heating or ventilation system control, and increasingly for home theater and computer networks. Some places allow the homeowner to install some or all of the wiring in a home; other jurisdictions require electrical wiring to be installed by licensed electricians only. Enquire Now.
Get Book. Download Residential Commercial And Industrial Electrical Systems Equipment And Selection books , Residential, Commercial and Industrial Electrical Systems is a comprehensive coverage on every aspect of design, installation, testing and commissioning of electrical systems for residential, commercial and industrial buildings. This book would serve as a ready reference for electrical engineers as well as bridge the gap between theory and practice, for students and academicians, alike. Volume 1: Equipment and Selection provides its readers a detailed description of various equipment typically used in electrical distribution system.
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Residential, Commercial and Industrial Electrical Systems: Equipment and Selection, Volume 1. Hemant Joshi. ISBN: Publication Date &.
Она состояла из легких в использовании программ для домашнего компьютера, которые зашифровывали электронные послания таким образом, что они становились абсолютно нечитаемыми. Пользователь писал письмо, пропускал его через специальную программу, и на другом конце линии адресат получал текст, на первый взгляд не поддающийся прочтению, - шифр. Тот же, кто перехватывал такое сообщение, видел на экране лишь маловразумительную абракадабру. Расшифровать сообщение можно было лишь введя специальный ключ - секретный набор знаков, действующий как ПИН-код в банкомате. Ключ, как правило, был довольно длинным и сложным и содержал всю необходимую информацию об алгоритме кодирования, задействуя математические операции, необходимые для воссоздания исходного текста.
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Они знают, как отсюда выбраться. На перекрестке он свернул вправо, улица стала пошире. Со всех сторон открывались ворота, и люди вливались в поток.
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Чуть впереди, у остановки, притормозил городской автобус. Беккер поднял. Дверцы автобуса открылись, но из него никто не вышел. Дизельный двигатель взревел, набирая обороты, и в тот момент, когда автобус уже готов был тронуться, из соседнего бара выскочили трое молодых людей.
Я знаю, что ты о нем думаешь.