Electric field strength vs magnetic field strength,emergency plan for active shooter kit,faraday cup capacitance - Reviews

What is a transmission line? A transmission line is a high-voltage overhead power line - the lines operated by National Grid for long-distance transmission of electricity. The magnetic field produced by a current in a conductor falls with distance from the conductor.
Although people living near high-voltage power lines are a group whose exposure is high and can often be calculated reasonably well, they are a small group. Raw dataIn the spirit of openness, most of the raw data used to plot the graphs of fields from overhead lines on this site are available as downloadable spreadsheets. Just as the capacitance of a capacitor had both a geometric and an operational definition, so does the inductance of an inductor. The self-inductance (or just inductance) of a coil is presented as where one henry of inductance means that the solenoid produces one weber of magnetic flux for each ampere of current traveling through its loops.
Just like one farad is a large amount of capacitance, one henry is a large amount of inductance. When current is running through the coils, a uniform magnetic field is produced down the center of the inductor. Notice that L, the inductance, is proportional to the square of the number of loops, directly proportional to the solenoid's cross-sectional area, and inversely proportional to the length of the solenoid. Faraday's Law states the emf induced is a coil is proportional to the rate of change of flux. Notice that the faster the current tries to change, the greater the inductor's "back emf." When the current is steady, , there will be NO back emf in the solenoid, or inductor. We will now use a graph of Flux vs Current to further examine the properties of an inductor. 2) In what aspects are the soil properties important when it comes to electrical installations?
7) What are the important factors that affect the maximum weight of the equipment to be installed (mounted) on a pole? 11) Pole class & guying are function of pole loading, what are the major loads acting on a pole? 16) What tools are used with disconnect switches & fuse cutouts to interrupt load currents? 21) What are the different methods of mounting (installing) distribution transformers on poles? 22) What are the main attachments (accessories) used to complete the installation of the overhead (pole mounted) distribution transformer? 23) What are the main components (accessories) that are mounted or included with the padmounted or vault type distribution transformers to complete its installation? 25) As used with transformers, what are the important curves that define the electric steel properties? 29) What are the different arrangements of coils used in distribution transformers and how does the cross section area of the wires look like? 32) When a transformer is energized, what are the losses encountered if it is not loaded & if it is loaded?
47) To make a splice that would last long, what are the conditions that have to be fulfilled while doing the splice?
50) Draw a sketch for an elbow & an elbow insert showing the main components of such a device? 64) What are the tests performed on the bulk material & those conducted on the complete insulator? 77) What are the office equipment commonly used & what are their approximate power consumption? 78) What are the required data to compare the total cost of the different lighting options or to calculate the payback period of the different installations?
The 3 properties of soil that affect the electrical installations are the hardness of the soil, its thermal resistivity & its electrical resistivity. The types of ultrasonic pulses are: longitudinal or compression pulses, transverse or shear (radial) pulses, surface or Rayleigh pulses, plate or Lamb pulses (in thin plates) & tangential pulses (in wood only). The poles that are made from concrete are used for street lighting, distribution and transmission line.
The hollow spun prestressed concrete poles have a high density concrete shell, completely, encasing a reinforcing cage containing prestressed high tensile steel wires.
Fibreglass poles when compared to wood poles are immune to freezing, rotting, damage from nails and pecking of birds. Steel structures (towers) have been used extensively to support sub-transmission and transmission line conductors. The major loads that may be acting on a pole are ice & wind loading which can be classified into either light, medium or heavy loading, transverse wind loading on the pole & conductors, pole line angle, longitudinal loading (along the line conductor) due to dead ending or a broken wire and vertical loading (weight of pole, cross-arms, pins, insulators, attachments, guys & ice covered wires).
When interrupted, the arc is formed between the metal horns of the circuit carrying the current.
Disconnect switches are air break switches, not equipped with arcing horns or other load break devices. When portable load break tools are used in conjunction with these switches, switching the following elements is possible: transformers, lines, cable and capacitors (with certain limitations). The oil filled units will have a fill plug, a drain valve, the oil gauge, the cable entrance, the steel tank, the spring operator, the mechanical interlock over the fuse compartment, grounding provision, parking stands and the hinged cover. These transformers can be fastened directly to the poles, hung from cross arms, mounted on racks or platforms or mounted on brackets attached to the poles. The high voltage bushing with the clamp type connector is connected to the primary (medium voltage circuit) and the low voltage cables are connected to spade type connectors. The distribution transformers rating for single phase varies from 10 KVA to 1MVA, for three phase 30 KVA to 2.5 MVA. The general arrangement of any transformer will have the following basic parts: an iron core consisting of laminated sheets, the primary and the secondary windings. The properties of the magnetic materials depend on: the chemical composition, fabrication process and heat treatment. The core construction can be any of the following, function of the rating and the design: wound, butt, or mittered (fig. A reminder, the exciting current can be broken down into a fundamental and a family of odd harmonics (using Fourier analysis).
The open coil uses a method whereby the transformer coils after being wound are immersed in an insulating varnish like silicone. The properties of the new oil to be used in transformers, the tests performed on the oil, the acceptable values from the different tests, the interpretation of the used oil test results and the instruments used to detect gases in oil are covered fully in ASTM and IEEE related standards. The volume of the generated gas and its rate depend on the temperature and the volume of the heated material. Undeground cables can be directly burried, can be put (pulled) in a conduit and burried (cable-in-a-conduit) or cables in conduits encased in concrete, fig. Rubber materials can be classified into vulcanized rubber & synthetic rubber materials (elatomers). These thermoplastic resins include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylenes (HDPE) and ethylene copolymers. The most common ways of failure in cables are: coring (or tracking) and thermal instability.
When the concrete encased designs are used, manholes have to be constructed and should have sufficient space to cut, splice and pull the cables. Bridges are used for the measurement of inductance, capacitance and loss (dissipation) factor, fig. The main methods that may be used are: Murray loop test, fall of potential test, dc charge and discharge test, induction test, impulse wave echo test and arc reflection.
The different types of terminations are: the fully taped, molded stress cone and tape, one piece molded, porcelain terminators, potheads and heat shrinkables. Faulted circuit indicators which can be installed in podmount transformers or switchgear can be classified accordingly: manually resettable, high voltage, current resettable and timed resettable. Self contained instruments are available for tracing the routes and the depth of hidden or buried cables.
The wires and cables over which electric energy is transmitted are made of copper, aluminum, steel or a combination of Cu and steel or AL and steel. When the same sizes of copper and aluminum conductors are compared, Al will have 60% of the copper conductor conductivity, 45% of copper tensile strength and 33% of copper weight.
The most important factors in sizing a line conductor are: the line voltage, the amount of power to be transmitted and the mechanical strength required. Concentric lay stranded cables can be classified according to their flexibility class AA, A, B, C and D where AA is the most rigid, bare and used in overhead systems, C and D being the most flexible. The properties of any insulator can be classified into: mechanical, electrical, environmental and maintenance. Fiberglass insulators (fiberglass rods with flexible skirts) are made up of fiberglass treated with polyester resin or more commonly with epoxy resins.
The properties of silicone to be used as insulators in power distribution systems are: high tear strength, high tracking and erosion resistance, has to be highly hydrophobic (water repellency property) or water repellent and has to recover quickly from any temporary hydrophobicity loss and has to resist UV aging.
The following points are worth investigating for the bulk material used as insulators for installation outdoors: thermal endurance, mechanical creep, long-term dielectric break down, partial discharge and as a complementary test to the partial discharge x-ray radiation test for larger cavities and voids.
The major components of the fuse holder of a fuse refill type fuse: the pull ring, upper and lower ferrule, glass epoxy fuse tube, blown fuse indicator, window and silencer. The typical parts that constitute a power fuse link are: the exhaust ferrule, the current transfer bridge, the fusible element, the arcing rod, the bore with the solid arc extinguishing material, drive spring, actuating pin, glass epoxy tube, the upper contact, the upper seal, arcing rod retainer. The current limiting type interrupts overcurrents when the arc established by the melting of the fusible element, is subjected to the mechanical restriction and cooling action of powder or sand filler, surrounding the fusible element. 1.Interruption of overcurrents is accomplished quickly, without the expulsion of arc products or gases, as all the arc energy is absorbed by the sand filler and, subsequently, released as heat. For vault mounted transformers, a series of current limiting and expulsion type with power fuse or fuse link mounted on the pole or the wall of the vault are most probably used as primary protection.
Energy management can be applied to the generation, transmission & distribution side of the electric network (utility side) as well as to the utilization side (user or consumer). The demand side energy management means the use of electric energy efficiently, thus increasing the profitability of the user or power consumer i.e. High efficiency motors are built with better quality material (steel) to reduce losses & improve efficiency.
Example for office equipment & their average consumption: desktop PC (130 W), monochrome monitor (30 W), colour monitor (60 W), laptop PC (10 W), dot matrix printer (50 W while printing & 25 while idle), laser printer (300 w while printing & 150 W while idle), inkjet printer (10 W while printing & 3 while idle), photocopier (300-1000 W), fascimile machine (100 W while transmitting & 15 W while idle), modem (20 W) and electric typewriter (130 W). GIS is a computer tool that allows the user to position, analyze and verify objects & events of geographic nature and produce an output in a geographic form (maps & tables). There are 5 main components that build a GIS, they are: hardware, software, data, users & methods. In England and Wales there are 7000 km of overhead transmission lines at 275 kV and 400 kV.
Where there is more than one current forming part of one or more electrical circuits, there is also partial cancellation between the magnetic fields produced by the individual currents, and that cancellation generally becomes better at greater distances. Ideal solenoids have a perfect flux-linkage - that is, the flux through any coil will encircle ALL of the coils. Later, Lenz added that the induced emf will be established in such a way as to oppose these changes and return the coil to its original condition.
An example of cohesive soil is clay as it is a fine grained soil, coarse grained soils are non-cohesive like sand.
The first property will affect the method of erecting the pole line & the selection of the anchors used in pole guying. The trunks and branches have, from the outside inwards the following: the bark, sapwood, heartwood and small core of soft tissue (in the centre). Preservatives that can be used are any of the following: creosote oil, ammoniacol copper fatty acid, pentachlorophenol and chromated copper arsenates (CCA). Concrete poles are more expensive than wooden ones, lower in insulation level, more difficult to climb, heavier to handle and more difficult to drill than wooden ones.
Prestressing produces poles with a high strength to weight ratios that is used for distribution lines.
Fibreglass poles are too expensive, but fibreglass components (like insulator supports) are reasonably priced.
Just to list a few examples: single phase primary circuit with the insulator on the top or side of the pole, 3 phase triangular armless with 1 insulator on the top and 2 on the sides, 3 phase triangular armless with the 3 insulators on the sides, vertical dead end and double circuit framing.
Guys are used wherever the wires tend to pull the pole out of its normal position and to sustain the line during the abnormal loads caused by sleet, wind and othe weather conditions. When insulators on wood poles become contaminated by dust or chemicals, then light rain fog or wet snow moistens the insulators, the poles and the crossarms (if available), these conditions will cause leakage currents to flow to the ground. The availablility of the material of the pole either wood or otherwise in the area where the pole line will be built or the pole will be erected is very important. Loading on poles must be calculated for the following conditions: crossings of railways, waterways & highways, crossings of other power or communication lines, pole angles and dead endings.


When current is interrupted, the arc is confined and extinguished in the interrupter (no external arc interruption or separate device is required). The different configurations of disconnect switches, as used on overhead systems, are: the branch feeder style, crossarm vertical, crossarm inverted, station vertical, station inverted and main feeder style. These switches are defined by the following parameters: insulation ratings (the nominal voltage in KV and the BIL in KV), rated continuous current in amperes, leakage distance in inches, dry arcing distance, disconnect gap in inches and cantilever strength of insulator in LBs.
Typically, for the air insulated type when the separable connectors are in place, the construction will have all energized parts enclosed in grounded (shield) enclosure (dead front).
How can a pad mounted switchgear be modified to operate & indicate remotely through a SCADA? The reason of having the cores laminated with insulation between the lamination is to reduce the eddy currents induced by the alternating magnetic flux. Saturation (magnetization) changes slowly by variation in chemical composition but is unaffected by fabrication (including impurities) or heat treatment. The varnish fills the air voids and coats the coil surface with about 2 mils(.002") protective coating. Gases due to composition of oil and solid insulation result from conductor temperature (due to load losses) and exposure to arc temperature. The breaking of carbon-hydrogen and carbon-carbon bonds result from the thermal or electrical faults under oil. The advantages to be gained with polyethylene are light weight, outstanding chemical resistance, mechanical resistance and excellent dielectric properties.
The first has the progressive coring starting at the conductor or the sheath and ultimately bridges the electrodes (conductor & sheath). The latter being a generator of high voltage pulses that are sent throughout the cable and produces arcing at the fault location, part of the pulse energy is reflected to the cable start where it is partially reflected into the fault.
The basic idea of operation is that if a fault to occur downstream this device all the indicators ahead of the fault will operate or set (as the fault current is flowing through them) and all the ones downstream the fault will not operate.
The location of underground cables is based on the principle of the concentric electromagnetic field surrounding a current carrying conductor. For the Al conductor to carry the same current as that of a Cu conductor its cross sectional area must be 66% higher than that of copper and in this case its tensile strength will be 75% and its weight will be 55% of that of the copper conductor. If Al conductor is installed in a copper connector, the Al (when heated due to the flow of the current) tends to flow out of the connector. When this type of connector is used with aluminum conductors, large spring-loaded pad is part of the installation to avoid cold flow.
Aluminum should physically be placed above copper when both materials are used in one connection. Other factors that may become relevant, depending on the application are: voltage regulation (drop through the line), power loss, span, total length of line. The mechanical characteristics can further be classified into: everyday loads, exceptional loads, design loads, cyclic loads, torsion and static loads, safety factors, single or multiple insulator strings, long term strength. Special types of clay are selected and mixed mechanically until a plastic-like compound is produced.
The materials are mixed and melted in an oven until a clear plastic-like product is produced. Rubber-like compounds are applied to the rods to fabricate suspension, dead-end and post type insulators. Continuous corona effect, close proximity of silicone insulators to large quantities of water vapour, spraying the insulator with salt water and rapid buildup of deposit on the surface of the silicone will have negative impact on the performance of the insulator. Surface erosion is mainly linked to UV radiation, corona and is enhanced by humidity and salt, thus testing for this effect for outdoor insulators is extremely important. The disconnecting fuse holder engages contacts supported on the insulating support and is fitted with a fuse link (with speed K-fast- or T-slow- as defined in ANSI 37.100). The operation of the fuse is goverened by two curves: the minimum melting and the total clearing. They can,also, reduce the thermal overloading due to the integration of the short circuit current over the period of the fault existence. The pad mounted transformers will have load or fault sensing (expulsion) type fuse that is accessible from outside the transformer to remove and replace and in series with this fuse a current limiting back-up fuse under the oil and is inaccessible without denergizing the transformers and removing the transformer from the site and probably breaking the welds of the cover, depending on the transformer design. It is a software that links information about where things are with information about what things are like.
The output results are laid out in geographic format that provides a much clearer and easy to understand presentation. Overall, the magnetic field is highest at the point of closest approach to the conductors and falls quite rapidly with distance. Continuing our comparison, recall that we used a gaussian surface to derive the capacitance of two parallel plates. In a real solenoid this only occurs when "the cross-sectional dimension of the windings are small compared to the coil's diameter or if a high permeability core is inserted to guide the flux" completely through all of the windings. Further subclassification to cohesive and non-cohesive is possible based on the origin or method of deposition or structure of the soil. Chemical preservatives are used to protect the wood from the attack of biological degraders like fungi, insects and marine organisms. Ultrasonic technology deals with the behavior of high frequency sound (beyond the range of human hearing). Fibreglass poles are used as streetlight poles supplied from an underground distribution system.
Subtransmision lines operating at voltages of 138KV or lower can be built on single wood-pole structures.
The leakage currents go to ground through a ground wire on the pole or the base of the pole.
Regarding wood poles, the factors that affect the choice of one type over the other are: the physical requirements of the poles, that are needed to construct the line, and the cost of shipment from the location where the species are grown.
Air switches can be further classified into: circuit breakers, air break, load break and disconnect switches.
These switches can interrupt line currents (load splitting, load dropping), transformer load and magnetizing currents, cable charging and load currents. In general, load break tools can be classified into a load interrupter tool and paralleling tool.
The vertical parts of the core are usually termed the limbs and the horizontal are the yokes. The wound (spiral) core may have the steel sheets cut to pre-determined lengths (commonly used) or sheets with no cuts, this is a common design with oil filled distribution transformers. Gases under low energy discharges and partial discharge (corona) conditions are formed, mainly by ionic bombardment. The arc under oil will have a high pressure gas bubble with the following fluids, from the outside toward the arc, inwardly (of the bubble): oil, wet oil vapour, super-heated oil vapour, hydrocarbons (C2H2 - acetylene) and hydrogen. The basic properties of polyethylenes can be modified with a broad range of fillers, reinforcements and chemical modifiers.
The second occurs when the power factor increases so rapidly with the rise of temperature in such a manner that a small rise in temperature increases the dielectric losses by a greater amount. In general, manholes, handholes and vaults are to be designed to sustain all expected loads which may be imposed on the structure. This method can be generalized and through the use of generators that give pulses of short duration and low voltages being transmitted through the cable, any deviations (cable start, splices, faults and cable end) will produce reflections. For the manual reset types, the intervention of the operator is required to reset the device. To identify and locate a cable, a predetermined frequency current from a generator is transmitted along the cable. When the connector cools down, the Al will contract with a diameter inside the copper connector slightly smaller than originally was. When conductors are connected to each other by connectors, the connection should provide an adequate current path under all expected operating conditions. They can, also, be classified according to the method of attaching the conductor to the insulator i.e. The electrical criteria are further divided into: clearances, BIL, power frequency flashover or withstand voltage (dry and wet), steep front wave, power arcs, leakage distance, contamination performance.
The rubberlike compound can be EPDM (Ethylene Propylene Diene, Modified) polymer or silicone elastomer. The degree of permanent loss of hydrophobicity is different for each of the conditions aforementioned. Surface erosion should be differentiated from pitting erosion (damage in depth of insulator over a small area). The typical refill construction of the distribution fuse cutout unit: current transfer bridge (connects the lower fusible end to the lower ferrule), fusible element, auxiliary arcing rod, auxiliary bore (where the arc is drawn and is interrupted for low fault currents), main arcing rod, main bore (where the arc is drawn and interrupted for moderate to high fault currents - above 100A), solid material arc extinguishing medium (boric acid for example), outer tube (of epoxy), fuse tube plug, upper terminal.
They may impose an overvoltage condition on the equipment connected due to the current chopping effect (forcing current to zero befoe natural current zero).
The partial range current limiting fuse operates without discharging flames, gases or any other by products of expulsive nature.
The main purpose of power system energy management is to achieve the goal of generating, transmitting & distributing electric energy efficiently & reliably.Its main functions are the supervision, the control and management of the electrical network in an integrated manner.
For industrials, the electric utility bill,usually, include a portion to the maximum demand (an average over a period of lets say 15 minutes) in KW reached for the billing period plus the energy consumption in KWH. The lower the motor horsepower the bigger the efficiency gap between the standard & the high efficiency one. These features of the GIS distinguishes it from other information technology systems and makes it a tool of great value to public as well as private users when it comes to presenting well explained, informative documents, to providing the required results of an analysis and showing the assumptions upon which the results are based, to forecasting the outcome based on the available factors & variables or in preparing strategic plans. For example a layer may have points that represent the cities in a region (or all the wells in an area), another layer of lines may represent all the streets in an area ( or watercourse in a region), a layer of areas can represent construction areas or similar use areas in a region. More detail on numbers of homes near power linesAveraged over the population, high-voltage power lines contribute only a small fraction of collective average exposure to EMFs, because so few people are exposed to them. In a REAL air-core solenoid, the flux density tends to decrease towards the ends of the coil since some of the flux lines "cut through" instead of encircle the final coils.
The third will affect the grounding system, including the grounding rods (electrodes) & grid (mat), that influences the current flow through the ground path and ground voltage under faulty conditions (flow of short circuit currents). The proper treatment of the wood can improve, significantly, the service life of the poles as it prevents deterioration. Frequencies used for testing metallic materials range from 2.25-10 MHZ, those for testing wood and other nonmetallic materials range 25-100 KHZ. The transportation issue of the poles have to be considered carefully due to the quantity of the poles required to build the line, the length of such poles as well as their weights. Air break switches are usually mounted on substation structures or on poles and are operated from the ground level.
The paralleling load breaking tool will create a temporary bypass jumper across the disconnect (in parallel with the permanent tap connection). The pole mounted transformers can be installed in clusters of 3 transformers attached to the supporting brackets of which the latter are attached to the poles. In general, these transformers are connected to the primary circuit through a current limiting fuse and a fuse cutout. 3 single phase connected to provide a delta or wye 3 phase configuration ) are quite common.
The two designs for the core are the core type where the iron core forming the limbs are surrounded by the windings and the shell type where the windings more completely surrounded by the iron (fig. If this type of material is used to build distribution transformers, lower core losses will produced. The butt (and lap) design will have two different sizes of sheets, the first make up the legs and the other to make the yokes.
The no-load losses are the result of the electric currents and magnetic fields necessary to magnetize the transformers core.
The products that result from thermal decomposition of oil impregnated cellulose material are carbon oxides (CO & CO2) and hydrogen (H2) or methane (CH4). Hard or vulcanized rubber is produced by mixing rubber with 30% sulphur, other softeners and antioxidation or other compounding agents.
Polyethylenes are considered easy to process: injection molding, sheet film extrusion, coating extrusion, wire and cable extrusion coating, blow molding, rotational molding, pipe and tube extrusion and others. The voltage to break down a certain insulation depends upon many factors such as duration of application, shape of electrodes, temperature, pressure, the presence of moisture and gaseous spaces. In its simplest form, the faulty cable is looped to an adjacent sound conductor of the same cross sectional area.
When the fault is passed, the cable will carry no current and nothing will be heard on the earphone. The observation on a CRT of the spacing of the reflections will indicate the fault location. The resulting magnetic field is then explored by means of an inductive probe or detector rod with the integral search coil and receiver.


This is, also, the reason for eliminating soldering of hard drawn copper, as this causes the reduction in the strength of the hard drawn wire. More extrusion will occur during subsequent loading cycles causing the contact resistance to increase. The connection should withstand all the combined mechanical and electrical stresses (vibration, tension, shear, heat).
For the environmental characteristics, the following are important: ageing under UV and dry arcing, type of contamination, corona, RIV, washing, corrosion of end fittings and temperature range. It became obvious that certain tests should be performed on the materials applied to the rods to be able to anticipate its performance over its long expected life time. The distribution transformers are protected by fuses (current limiting and expulsion types). This series of fuses provides the current - time characteristics of a co-ordinated full range fuse, C.L. It includes SCADA (system supervisory control & data acquisition) & DAC (distribution automation & control). The user enter different geographic features on different layers (this characteristic is similar to CAD software packages). The preparation of maps and reports based on geographic analysis are not new activities, but with the GIS the outcome is produced faster, consistent & accurate.
Each of the geographic features will have its own set of attributes (characteristics of such feature) that are described by numbers, characters, images and CAD drawings (typically stored in tabular format and linked to the feature by a user defined identifier).
Hence why we experimentally are always directed to measure the B-field of a solenoid in the center of its middle coils.
Soils do not necessarily retain consistency at various depths, they are in layers of different thickness of unlike soils.
Ultrasonic pulses are produced by transducers and during the test the pulses are received by other transducers found on the receiving end.
The main components of the anchor guy assembly are: galvanized machine bolt with nut, locknut, square curved galvanized washer, galvanized steel guy wire, porcelain guy strain insulator, prefabricated guy dead-end grips, plastic guy guard, angle thimbleye, eyenut, steel anchor rod, power installed screw anchor.
When the medium in the dry zone (example air) is subjected to dielectric stress (voltage gradient) that exceeds the dielectric strength of this gap, an arc will be established. The strength of the poles have to be enough to withstand all the expected loads that the poles will be subjected to during its expected life span. To protect the transformers against lightning or voltage surges, the primary of the transformer will have a lightning arrester connected across it and the ground.
The cooling rate of the liquid alloy to obtain the amorphous metal structure is in the order of 1 million degrees per second.
In this design, the gaps between the different steel parts (in the flux path) may be the reason for the noise and the increase in the required ampere-turns to achieve the desired (rated) flux density. The magnetizing current equals the exciting current minus the core loss component which means it is equal to all the harmonics plus the out of phase fundamental component. The no load losses are present as long as the transformer is kept energized (it is independent of the transfomer loading).
Thus, to use the presence of the gas in the transformer oil as an indication of the presence of a fault, three distinctive types of faults have to be defined. The end result is an insulating material which is rigid, resilient and does not absorb moisture.
PVC can be classified into general purpose, hard grade PVC (has less amount of placticizer) and heat resisting PVC.
There are two main methods by which a more uniform distribution of stress may be achieved: by the introduction of intersheaths and with layers of insulating material with different dielectric constant (e).
For crosslinking of polyethylene there are a few methods in us today: peroxide systems, radiation and silane bridges formation. The manholes are generally built of reinforced concrete or brick and the covers are made of steel. Note that cos f = tan d = wcr; where c is the capacitance of the insulation and r is the resistance of the insulation & w = 2 pi f, f is the frequency of the applied voltage. Across the open ends, a galvanometer is joined and parallel with it a resistance box with two sets of coils. The limitation of this method is when the fault resistance is high (higher than ten times the cable characteristics impedance which varies in the range of 30 to 50 ohm).
The contact resistance & consequently the heat generated at the connector (I2R) keeps increasing until failure occurs.
Connectors when compressed over a conductor a specific range of % compaction must be attained in the range of 5 to 15 % of thhr conductor area. Materials of conductor and connectors have to be compatible so load cycling (cold flow) would not produce hot spots or failures. The final property of an insulator is maintenance, it comes down to ease or difficulty of handling or the need for special precautions. Medium voltage fuses (2.4 to 72kV) can be classified according to the following, they either fall under the distribution fuse cutouts or power fuses. The gas ionized (liberated), when the liner is exposed to the heat of the arc (as a result of the melting of the link), is then deionized (at current zero).
Before, only few persons had the knowledge and were able to access these geographic data in order to make decisions or solve problems. Soils in general can be classified according to their hardness into 9 general classes from 0 to 8, 0 being the most solid (sound hard rock) like granite, basalt, massive limestone and 8 the softest like swamp and miscellaneous fills. The arc, if close to combustible material like wood, it will ignite the wood in the dry area. There is another type of pole mounted transformers which is the completely self protected one (CSP). The material of the core is either the grain oriented silicon steel or the amorphous alloys.
It is the eddy current component in the core losses that increases with the increase in the thickness.
The mittered core will have the sheets for the legs and yokes cut at 45° in order to have the flux path always in the direction the steel was rolled (grain oriented).
The coils are of the pre-wound (formed) construction and can be of the cylindrical or disc type.
At constant magnetic induction and magnetic strength field, the total losses decrease with the increase in the permeability. Auxilliary losses (like fans energy consumption that is charged to the demand) are not available with the distribution transformers but are present in the substation transformers above 5MVA ratings. The three types are: thermal, electrical (low intensity discharges) and high intensity electrical arcs.
When it comes to synthetic rubber materials (elastomers) known as rubbers, they can be classified into: general purpose synthetics which have rubber like properties and special purpose synthetics which have better properties than rubber with respect to fire and oil resisting properties. The curing of the extruded cables takes place in air at ambient temperatures, in a hot water bath or in a steam room. The opening leading from the street to the manhole chamber is called the chimney or throat. Power factor of single core cable: suppose that the dielectric has a resistance R which is independent of the stress and may be considered as constant throughout the cable upon the application of an alternating voltage of frequency f, there will be an in phase current equal the voltage divided by the resistance of the insulation per cm length.
With high impedance faults, urning the fault into a lower resistance fault and cable radar method is used to obtain the fault location. For the current type, after repairs have been done, the current flowing in the circuit reaches a minimum pre-adjusted value (eg. Annealed or soft drawn copper is used for grounds or special applications where bending and shaping the conductor is necessary.
Excessive compaction will result in conductor deformation and light compaction may not provide sufficient pullout strength. Protection against weather conditions, like water stop and corrosion protection, is provided whenever possible. Thus certain layers (information) can be suppressed if they are irrelevant to the task at hand. Each geographic feature will also have its exact geographic position expressed as coordinates, eg.
Soil can be tested by soil test probes which give readings in LB-inch per probe pitch (the reading is at the end of the pitch).
Wood defects can be related to either decomposition of wood fibre by fungi (decay) or to breakdown of cell walls as a result of applied stress beyond the yield stress of the cell of the wall material ( mechanical destruction). Primary fuses and lightning arresters are included with the transformer, thus there is no need to any external protective device except for a current limiting fuse.
Hot rolled or cold rolled steels are used in transformers with regular grain or high permeability grain oriented properties.
The total owning cost of a transformer constitute of the initial cost (purchasing price), cost of no-load losses (over the expected life of the transformer) and load losses (over the expected life of the transformer) and may be the maintenance cost (over the expected life of the transfomer).
The failure in cables with this insulating material can be attributed to the water absorption property of XLPE. To minimize cold flow any or all of the following should be observed: use compression type aluminum connectors, use Belleville washers, the aluminum connectors must have substantial mass to run cool and the contact area between the conductor strands and the connector is to be maximized. A digital map created by GIS will have points (dots) that represent features on a map like cities, polygons (small areas) that represent features such as lakes and arc (lines) that represent features like roads.
Cartesian - planar (x,y), 3-dimension (x,y,z), vector, which is stored with its attributes.
The increase of the grain size number reduces the losses, as well as the increase in percent silicon (increase in the resistivity) reduces the losses.
The losses cost and maintenance (if included) are presented as first cost (present value) in order to make the evaluation of the total owning cost of the different available transformers for each size or rating (of transformer) possible. The thermal faults that will cause the oil temperature to rise to up to 500 deg.C will produce H2, CH4 and trace quantities of C2H4 & C2H6. In the polymerization process, the double bond connecting the carbon atoms is broken and these bonds reform with other ethylene molecules to form long molecular chains. This opening has to be large enough for a man to enter on a ladder and also to pass the equipment needed for splicing and testing. The losses with alternating currents are caused by absorption phenomena and is usually much less than those caused by d.c. Cement growth, which may result from chemical reaction between the cement and the metal parts, can cause stresses that can crack the insulator. The GIS software can be considered a package made up of sub packages that can communicate and understand each other. For high efficiency transformers or motors the steel used would have silicon in the 4-5% range.
An elastomer is defined, per ASTM, as a polymeric material which at room temperature can be stretched to at least twice its original length and upon immediate release of the stress it will return quickly to approximately its original length.
High density polyethylene resins have molecular chains with comparatively few side chain branches. The pulling rope is attached to the cable by means of a woven cable grip, sometimes called basket grip, or by means of a clevis or eye. After the windings were prepared, the coils are placed in a vacuum chamber and evacuated, then flooded under vacuum with a low viscosity epoxy resin. To prevent injury to the cable by scraping on the manhole frame or at the duct opening, a feeding tube (guiding tube) is sometimes used. When an indicator operates, it will show the section of the buried cable that may be faulty.
Thermal decomposition of cellulose and other solid insulating materials will produce CO, CO2 and water vapour. To protect the cable from excessive tension during pulling in, the cable is lubricated with a compatible material to the jacket.
Certain designs come with attachments to alleviate potential nuissance resetting or setting like inrush currents when energization of transformers or due to reclosing actions of reclosures or station circuit breakers. After connecting the tool to the disconnect as previously mentioned, the universal pole is pulled downward (firmly and steadily) and as the tool is extending to its maximum length, the disconnect is opened and the current is diverted through the tool. The cable is drawn into the duct by means of a winch or capstan The winch is usually mounted on a truck or a portable cable puller located near the manhole or the riser (pole) conduit, at pulling end. At a predetermined point in the tool opening stroke, its internal trigger trips, the charged operating spring is released, the internal contacts are separated and the circuit is interrupted.
For electrical low intensity discharges under oil, H2, CH4 and traces of C2H2 will be produced.
A wide range of property grades exists by varying the relative amounts of styrene and butadiene.



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