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High Resistance Connection
A high-resistance connection (HRC) is a hazard that results from loose or poor connections in traditional electrical accessories and switchgear which can cause heat to develop, capable of starting a fire. Glowing connections occur when relatively high current exists in a relatively large resistance object. Heat comes from power dissipation. This energy, when dissipated in a small junction area, can generate temperatures above 1000 °C (1800 °F) and can ignite most flammable materials. An example extract from the National Union of Teachers (NUT) Fire Safety Brief: :* Electrical equipment should be regularly maintained by competent people. Machines should not be allowed to overheat. Care should be taken not to cover machines while they are switched on as this is particularly likely to cause overheating. Trailing cables should be regularly checked for damage. Loose or poor connections in traditional electrical accessories and switchgear can cause heat to develop capa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Switchgear
In an electric power system, a switchgear is composed of electrical disconnect switches, fuses or circuit breakers used to control, protect and isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults downstream. This type of equipment is directly linked to the reliability of the electricity supply. The earliest central power stations used simple open knife switches, mounted on insulating panels of marble or asbestos. Power levels and voltages rapidly escalated, making opening manually operated switches too dangerous for anything other than isolation of a de-energized circuit. Oil-filled switchgear equipment allows arc energy to be contained and safely controlled. By the early 20th century, a switchgear line-up would be a metal-enclosed structure with electrically operated switching elements using oil circuit breakers. Today, oil-filled equipment has largely been replaced by air-blast, vacuum, or SF6 equipmen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Power Dissipation
In thermodynamics, dissipation is the result of an irreversible process that takes place in homogeneous thermodynamic systems. In a dissipative process, energy (internal, bulk flow kinetic, or system potential) transforms from an initial form to a final form, where the capacity of the final form to do thermodynamic work is less than that of the initial form. For example, heat transfer is dissipative because it is a transfer of internal energy from a hotter body to a colder one. Following the second law of thermodynamics, the entropy varies with temperature (reduces the capacity of the combination of the two bodies to do work), but never decreases in an isolated system. These processes produce entropy at a certain rate. The entropy production rate times ambient temperature gives the dissipated power. Important examples of irreversible processes are: heat flow through a thermal resistance, fluid flow through a flow resistance, diffusion (mixing), chemical reactions, and electric cu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Union Of Teachers
The National Union of Teachers (NUT; ) was a trade union for school teachers in Education in England, England, Education in Wales, Wales, the Channel Islands and the Isle of Man. It was a member of the Trades Union Congress. In March 2017, NUT members endorsed a proposed merger with the Association of Teachers and Lecturers to form a new union known as the National Education Union, which came into existence on 1 September 2017. The union recruited only Qualified Teacher Status, qualified teachers and those training to be qualified teachers into membership and on dissolution had almost 400,000 members, making it the largest teachers' union in the UK, United Kingdom. Campaigns The NUT campaigned on educational issues and working conditions for its members. Among the NUT's policies in 2017 were: * Fair pay for teachers * Work-life balance for teachers * Against academy (England), academies * Abolition of National Curriculum Tests (SATs) * One union for all teachers The NUT offe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aluminum Wire
Aluminum building wiring is a type of electrical wiring for residential construction or houses that uses Aluminum conductor, aluminum electrical conductors. Aluminum provides a better conductivity to weight ratio than copper, and therefore is also used for wiring Electric power transmission, power grids, including Overhead power line, overhead power transmission lines and Electric power distribution, local power distribution lines, as well as for power wiring of some airplanes. Utility companies have used aluminum wire for electrical transmission in power grids since around the late 1800s to the early 1900s. It has cost and weight advantages over copper wires. Aluminum wire in power transmission and distribution applications is still the preferred material today. In North American residential construction, aluminum wire was used for wiring entire houses for a short time from the 1960s to the mid-1970s during a period of high copper prices. Electrical devices (outlets, switches, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fuse (electrical)
In electronics and electrical engineering, a fuse is an electrical safety device that operates to provide overcurrent protection of an electrical circuit. Its essential component is a metal wire or strip that melts when too much current flows through it, thereby stopping or interrupting the current. It is a sacrificial device; once a fuse has operated it is an open circuit, and must be replaced or rewired, depending on its type. Fuses have been used as essential safety devices from the early days of electrical engineering. Today there are thousands of different fuse designs which have specific current and voltage ratings, breaking capacity, and response times, depending on the application. The time and current operating characteristics of fuses are chosen to provide adequate protection without needless interruption. Wiring regulations usually define a maximum fuse current rating for particular circuits. Short circuits, overloading, mismatched loads, or device failure are the prime ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Residual-current Device
A residual-current device (RCD), residual-current circuit breaker (RCCB) or ground fault circuit interrupter (GFCI) is an electrical safety device that quickly breaks an electrical circuit with leakage current to ground. It is to protect equipment and to reduce the risk of serious harm from an ongoing electric shock. Injury may still occur in some cases, for example if a human receives a brief shock before the electrical circuit is isolated, falls after receiving a shock, or if the person touches both conductors at the same time. If the RCD device has additional overcurrent protection integrated in the same device, it is referred to as RCBO. An earth leakage circuit breaker may be a RCD, although an older type of voltage-operated earth leakage circuit breaker (ELCB) also exists. These electrical wiring devices are designed to quickly and automatically isolate a circuit when it detects that the electric current is unbalanced between the supply and return conductors of a ci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Connectors
Components of an electrical circuit are electrically connected if an electric current can run between them through an electrical conductor. An electrical connector is an electromechanical device used to create an electrical connection between parts of an electrical circuit, or between different electrical circuits, thereby joining them into a larger circuit. Most electrical connectors have a genderi.e. the male component, called a ''plug'', connects to the female component, or ''socket''. The connection may be removable (as for portable equipment), require a tool for assembly and removal, or serve as a permanent electrical joint between two points. An adapter can be used to join dissimilar connectors. Thousands of configurations of connectors are manufactured for power, data, and audiovisual applications. Electrical connectors can be divided into four basic categories, differentiated by their function: * ''inline'' or ''cable'' connectors permanently attached to a cable, so i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Safety
Electrical safety testing is essential to make sure electrical products and electrical installations are safe. To meet this goal, governments and various technical bodies have developed electrical safety standards. All countries have their own electrical safety standards that must be complied with. To meet to these standards, electrical products and electrical installations must pass electrical safety tests. Some types of electrical safety tests include: *dielectric withstand test (also called a hipot test) *insulation resistance test (IR test) *earth continuity test *leakage current test Electrical safety tests are described in IEC 60335, IEC 61010, AS/NZS 3000, NFPA 70, BS 7671, and other national and international standards.\ Electrical Safety tests Dielectric voltage withstand test A dielectric voltage withstand test (also known as a hipot test) is done by applying a voltage higher than operating voltage to the device or installation under test. In this test, the el ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
