Internal And External Cable Wiring Types Pdf
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- Different Types of Wiring Systems and Methods of Electrical Wiring
- Different Types of Wiring Systems and Methods of Electrical Wiring
- Electrical cable
More often than not, the terms wire and cable are used to describe the same thing, but they are actually quite different.
Different Types of Wiring Systems and Methods of Electrical Wiring
Electrical wiring in the United Kingdom is commonly understood to be an electrical installation for operation by end users within domestic, commercial, industrial, and other buildings, and also in special installations and locations, such as marinas or caravan parks. Electrical wiring is ultimately regulated to ensure safety of operation, by such as the building regulations , currently legislated as the Building Regulations , which lists "controlled services" such as electric wiring that must follow specific directions and standards, and the Electricity at Work Regulations The detailed rules for end-use wiring followed for practical purposes are those of BS Requirements for Electrical Installations.
IET Wiring Regulations , currently in its 18th edition, which provide the detailed descriptions referred to by legislation. UK electrical wiring standards are largely harmonised with the regulations in other European countries and the international IEC standard. However, there are a number of specific national practices, habits and traditions that differ significantly from other countries, and which in some cases survived harmonisation.
These include the use of ring circuits for domestic and light commercial fixed wiring, fused plugs , and for circuits installed prior to harmonisation, historically unique wiring colours. The standard wiring colours in the UK are as of [update] the same as elsewhere in Europe and follow international standard IEC The standard colours in fixed wiring were harmonised in with the regulations in other European countries and the international IEC standard. For a transitional period April — March either set of colours were allowed but not both , provided that any changes in the colour scheme are clearly labelled.
From April , only the new colours should be used for any new wiring. The UK changed colour codes three decades after most other European countries, as in the change of neutral and phase colours was not considered safe by the IEE.
Blue, previously used as a phase colour, is now the colour for neutral. Black, which was previously used for neutral, now indicates a phase. Household wiring does not usually use three-phase supplies and the clash only occurs in three-phase systems. Wiring to the old standard can be detected by use of a red wire.
The new standard colour code does not use red. Where new wiring is mixed with old, cables must be clearly marked to prevent interchange of phase and neutral. There is a long history of colour changes; prior to white was used instead of yellow as the second phase, and before World War II, a black earth and a green third phase in place of green earth and white phase was permitted. The regulations permitted and still do the use of any wire colour that is not an earth colour, providing it is unambiguously identified at all connections by clear labelling or by correctly coloured over-sleeving.
It was not uncommon on commercial builds of the s with a three phase supply for the phase colours red, yellow, blue to be used throughout single phase sub circuits thus indicating the phase origin of the supply, in this case no over-sleeving was used and can give rise to confusion when encountered today. Direct current mains supplies are only of historical interest in the UK but the colour coding was red for live and black for earthed regardless of the polarity.
Hardly any loads were polarity sensitive when direct current systems were introduced principally incandescent lighting, heating systems or series direct current motors and it was considered more important to identify the live wire than the polarity. Where all three wires were available, the historical colour code was red positive , black middle and white negative. The negative line changed to yellow in , and then to blue in The colour of the outer sheath is currently grey, or white for low halogen material.
Previously cables from different manufacturers were available variously in grey or white, with no significance attached to the sheath colour. The grey colour was adopted by cable manufacturers to match older lead sheathed flat cables, with some manufacturers using a silver grey polyvinyl chloride. UK fixed wiring circuits, unlike those found in almost all other countries, make widespread use of ring circuit designs, as well as radial circuit designs often seen in other countries.
This was one of the recommendations of the Electrical Installations Committee, convened in as part of the Post War Building Studies programme, which in determined that the ring final circuit offered a more efficient and lower cost method to support a greater number of sockets. Lighting circuits, which typically have lower power requirements, are usually radially wired, confusingly sometimes called "loop" wiring. In both ring and radial circuits, the circuit wiring starts at a consumer unit or distribution board , and traverses in turn a number of sockets or devices point-to-point style , before terminating.
The difference is that a radial circuit simply ends upon reaching the last connected device in any branch, whereas in a ring circuit the termination is made by rejoining the end of the circuit from the last device back to its starting point. A ring circuit therefore forms a continuous ring, while a radial may be a simple linear chain, though it may split and have several branches. This means that in a ring there are two independent paths from the supply to every device.
Ideally, the ring acts like two radial circuits proceeding in opposite directions around the ring, the dividing point between them dependent on the distribution of load in the ring. If the load is evenly split across the two directions, the current in each direction is half of the total, allowing the use of wire with half the current-carrying capacity. The innovation that made ring circuits feasible in the UK was the fused plug to BS with its "square pin" format. BS plugs may be fitted with a range of fuses up to 13A.
This means that every load plugged in is covered by an appropriate protective device at the socket, so that the whole ring may then be protected by usually a 32A breaker at the distribution panel. In contrast, circuits feeding any other kind of socket outlet need to be protected by a breaker that will not allow the socket's rating to be exceeded, and so the radial circuits generally used with outlets such as the European Schuko style outlets generally have to be protected by a 16A breaker at the distribution panel; this limits the total load on the circuit and hence such circuits tend to have fewer socket outlets.
Cables are most commonly a single outer sheath containing separately-insulated line and neutral wires, and a non-insulated protective earth to which sleeving is added when exposed.
Standard sizes have a conductor cross sectional area of 1, 1. Sizes of 1 or 1. The earthing conductor is uninsulated since it is not intended to have any voltage difference from surrounding earthed articles. Additionally, if the insulation of a line or neutral wire becomes damaged, then the wire is more likely to earth itself on the bare earth conductor and in doing so either trip the RCD or burn the fuse out by drawing too much current.
Earthing and bonding are used together to provide shock protection by avoiding a dangerous combination of magnitude and duration of the voltage to which people may be exposed in the event of a fault within the installation or outside the installation. Exposure may be from e.
Examples of faults are an insulation failure between a line conductor and a metallic frame of an appliance within the installation, a break in a combined protective-earth and neutral conductor in the supply, or an insulation fault in the supply transformer causing the whole low-voltage system to rise in potential.
In the event of an insulation fault from a live conductor to an appliance's metal frame an ECP , the frame could—if not so connected—be dangerous if touched by someone who is also for example standing outside on the ground, or standing inside on a concrete floor, or holding a tap whose pipe connects it electrically into the ground.
Protective earthing limits the combination of magnitude and duration of the dangerous voltage that could exist between the ECP and the earth itself. In conventional installations in the UK the voltage between an appliance frame and the earth itself during a zero-impedance fault has a dangerous magnitude: it might be reduced to about half of the V line-earth voltage, which is well above the 50 V usually accepted as safe for an AC system, or it might be nearly V in a TT system with a poor earth electrode for the installation.
The duration of this voltage must therefore be limited, which is done by "automatic disconnection of supply" ADS either by overcurrent protection devices OCPDs , or by residual current devices RCDs that specifically detect the current escaping from the intended circuit, allowing them to have a far lower tripping current. In TT systems it is almost always necessary to have an RCD, as earth electrodes usually have many times higher resistance than a typical supply cable, so earth-fault currents are relatively low.
However, the connection to the earth itself is always relevant, since the earth forms a mildly conductive surface that we cannot easily avoid e. In TT systems the installation's earth electrode needs to have low enough impedance to operate protection if a safe voltage usually taken as 50 V between the installation and remote earth is exceeded; in TN systems the system's neutral point needs a low resistance connection to earth to prevent a fault between a line conductor and some unintended earth electrode from displacing the neutral-point potential to a dangerous level compared to the earth.
Bonding is the connection of conductive parts together, to reduce the voltage between them. This is an important measure for electric shock protection. When this protective function is the purpose of bonding, BS describes the bonding by the term "protective equipotential bonding"; this does not mean that the bonding guarantees perfect equipotentiality, but just that it reduces the differences of potential.
In the following, this formal term is abbreviated to "bonding". Without adequate bonding, dangerous voltages could arise between conductive parts that can be touched simultaneously, either due to problems outside the installation, or to faults in the installation.
These parts could otherwise introduce potentials that are different from the potential of the installation's earthing system. The main bonding avoids dangerous differences in potential being introduced into the installation, between e.
Supplementary bonding connects simultaneously touchable conductive parts in local parts of an installation: the parts may be pairs of ECPs on different circuits, or an ECP and extraneous conductive parts. This reduces the voltage between them, even in fault conditions. Supplementary bonding is particularly used in situations such as bathrooms, where body resistance is low and therefore requires magnitude and duration of touch voltages to be very limited.
In special circumstances not domestic installations bonding with deliberate lack of connection to earth earth free local equipotential bonding may be used.
Bonding, by the IEC terminology used in BS , should not be seen as just an extra to earthing. In recent US practice, which differs considerably from IEC principles and terminology, "bonding" is used more widely as a term for all the aspects of earthing that are not literally connections with the earth itself "grounding" ; so the connection of protective earth conductors to the supply neutral since the TN-C-S system is the only permitted form in their residential installations is now named bonding rather than earthing.
This is not the case in the UK. A domestic supply typically consists of a large cable connected to a service head, the sealed box containing the main supply fuse, treated as the supply to the premises. Separate line and neutral cables tails go from here to an electricity meter , and often an earth conductor too.
More tails proceed from the meter into the consumer side of the installation and into a consumer unit distribution board , or in some cases to a Henley block a splitter box used in low voltage electrical engineering, slang named for W. The distribution board a. In a UK-style board, breaker positions are numbered top to bottom in the left-hand column, then top to bottom in the right column.
Three phase power is usually supplied as needed, for commercial and industrial premises. While three phase loads take balanced power from the three phases, any single phase loads are distributed to ensure equal loading of the three phases. Each row of breakers in the distribution board is fed from a different phase L1, L2, and L3 , to allow 3-pole common-trip breakers to have one pole on each phase.
Single-pole switches are most commonly used to control circuits. These switches isolate only the line conductor feeding the load and are used for lighting and other smaller loads. For larger loads like air conditioners , cookers, water heaters and other fixed appliances a double-pole switch is used, which isolates also the neutral, for more safety. A three-pole isolator or circuit breaker is used for three-phase loads, for devices with both permanent and switched supplies such as bathroom extractor fans and also at the distribution board to isolate all the phases as well as the neutral.
Many accessories for electrical installations e. Accessories in the BS format are only available in a comparatively limited range of designs and lack the product diversity and design sophistication found in other European markets.
The UK installation-accessory industry is therefore occasionally criticised for being overly conservative. For higher currents or three-phase supplies, IEC sockets are to be used instead.
Flexible appliance cords require protection at a lower current than that provided by the ring circuit overcurrent protection device. In the case of permanently connected equipment, a fused connection unit FCU  to BS is used, this may include an isolator switch and a neon bulb to indicate if the equipment is powered.
Note, it is not intended that the fuse should protect the appliance itself, for which it is still necessary for the appliance designer to take the necessary precautions. Multiple socket accessories may be protected with a fuse within the socket assembly. The selection of conductors must be made taking into consideration both the maximum voltage drop allowed at the load end and also the current carrying capacity of the conductor.
Conductor size and voltage drop tables are available to determine the selection, which will be based on the load current supplied. The choice of circuit breaker is also based on the normal rated current of the circuit. Modern circuit breakers have overload and short circuit current protection combined. The overload protection is for protection of the equipment against sustained small-to-medium increase in current above the rated current, while short circuit protection is for the protection of the conductors against high over-currents due to short circuits.
For domestic circuits the following choices are typically adopted for selecting conductor and circuit breaker sizes. For distribution boards the incomer circuit breaker rating depends on the current demand at that board. For this the maximum demand and diversity are taken into consideration, based on which the probable current is calculated.
Diversity is the condition that all appliances are not likely to be working all at the same time or at their maximum ratings.
Different Types of Wiring Systems and Methods of Electrical Wiring
Electrical Wiring is a process of connecting cables and wires to the related devices such as fuse, switches, sockets, lights, fans etc to the main distribution board is a specific structure to the utility pole for continues power supply. They are discussed as follows:. In this method of wiring, connections to appliances are made through joints. These joints are made in joint boxes by means of suitable connectors or joints cutouts. It is of course but the money you saved from buying cables will be used in buying joint boxes, thus equation is balanced.
Unarmored Cable similar to US TC type cables but with fully extruded fillers. protect intrinsically safe circuits against external electrical or magnetic fields backed Polyester tape with a stranded copper drain wire mm², inner sheath of.
Electrical wiring in the United Kingdom is commonly understood to be an electrical installation for operation by end users within domestic, commercial, industrial, and other buildings, and also in special installations and locations, such as marinas or caravan parks. Electrical wiring is ultimately regulated to ensure safety of operation, by such as the building regulations , currently legislated as the Building Regulations , which lists "controlled services" such as electric wiring that must follow specific directions and standards, and the Electricity at Work Regulations The detailed rules for end-use wiring followed for practical purposes are those of BS Requirements for Electrical Installations. IET Wiring Regulations , currently in its 18th edition, which provide the detailed descriptions referred to by legislation.
The term " coaxial " refers to the inner conductor and the outer shield sharing a geometric axis. Coaxial cable is a type of transmission line , used to carry high-frequency electrical signals with low losses. It is used in such applications as telephone trunklines, broadband internet networking cables, high-speed computer data busses , cable television signals, and connecting radio transmitters and receivers to their antennas. It differs from other shielded cables because the dimensions of the cable and connectors are controlled to give a precise, constant conductor spacing, which is needed for it to function efficiently as a transmission line. Coaxial cable was used in the first and following transatlantic cable installations, but its theory wasn't described until by English physicist, engineer, and mathematician Oliver Heaviside , who patented the design in that year British patent No.
An electrical cable is an assembly of one or more wires running side by side or bundled, which is used to carry electric current.
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