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Power Generation Book Co-generation is growing market as demand for reliable energy grows. Book by Singh covers the basics, and the engineering math. Future business and industry leaders should be aware of the complexity and variability of electricity. Buy Related Books: Power generation by Singh 3-phase power generation book at Amazon Electric Power generation books at Amazon 3-phase wiring books at Amazon Overhead conductor Resource: Basic How to wire 3-phase with illustrations and .pdf resources |
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Lineman's Books Practical application and terminology/ not mathematical Buy from my affiliate links Lineman's electric book Overhead conductor |
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Solar
power books Learn the basics with tips and help for professional and beginner alike Buy from my affiliate links: Solar power books Web strap ratchet lever hoists lineman’s puller web strap web strap puller lever hoist hot stick hoist options Tension Puller pullers and tensioners Compression clamps Jumper clamps Power line tools/ pdf Arc protective clothing pdf |
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Basic electric Book Buy Best basic electric book Electric book series Basic electricity/ AC DC/ Basic electric book/ very detailed Wiring a house Resource: Learn from my simple illustrations and wiring: Do it yourself electric Resources: Water heater formulas/ pdf Water heater formulas 2/ pdf Troubleshot household electricity What is 3-phase See inside household electricity Basic home electricity Figure volts amps watts |
 Larger image Power plants are rated by megawatt output, or 1,000,000 VA (volt amps). Up to 25% of generation can be used to operate plant which boils water into steam, using the steam explosion to accelerate a turbine which spins an electromagnet past 3 coils of wire. See image Each coil becomes energized with electric potential. A wire is connected to one end of each of the 3 coils, and those 3 wires become the 3 Hot wires found in 3-phase power. The other ends of the 3 coils are joined together to form the Neutral wire that travels with the hot wires, and is bonded to the ground rod array located under the power plant and switchyard, and is bonded to the ground at each tower, pole, substation, and installation along the way. Resource: Power-Plants.pdf |
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 Larger image Helical Rod Spacers hold the two wire bundles apart from each other while stabilizing the lines. |
Power plant switchyard
to 3-phase 270,000-500,000 volt Transmission Power lines leaving plant ... with coal-fired power plant and switchyard in background These lines estimated to carry 270,000+ volts en route to Houston and surrounding area. Parts needed for transmission, such as insulators, wire, bolts, assemblies etc are rated by voltage and strength. EHV extra high voltage, roughly defined as 345,000– 765,000 Volts. UHV ultra high voltage, > 800,000 volts Resources: Overhead-Installation-Guide.pdf Mechanical design of overhead power lines Hubbell suspension support .pdf Larger image  |
 3-phase high-voltage transmission Larger image |
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3-phase Transmission Vibration dampers are added to each line as it nears a suspension point. Dampers are used to reduce line movement caused by wind loading. Other protections include armor rods installed where the wire is held by the suspension clamp. ''ARMOR RODS are designed to protect cable against bending, compression, abrasion, and flash-over. They are also used to repair damaged aluminum-based conductors and restore the conductors' mechanical strength and conductivity.'' Helical Vibration Dampers: spiral vibration dampers are used for smaller size conductors: shield wires, guy wires etc. Corona ring/ corona Shield Resource: Vibration dampers Hubbell damper-armor-rods-line-protection.pdf Armor rods .pdf Transmission line repair manual |
 2 Conductor Horizontal I-String Materials for power line assemblies vary by need and include: Polymer, Toughened Glass Galvanized Forged Steel, Steel, Galvanized Ductile Iron, Aluminum, Aluminum Alloy Larger image |
3-phase Transmission Suspending dual wires from transmission tower Assembly for suspending a two conductor bundle from a transmission tower. The dual wires are held 18" apart using two suspension clamps attached to a yoke plate. Transmission wires are protected from damage using armor rods and vibration dampers. The assembly is made to move and sway with the wind load encountered by all overhead electrical installations. Resources: Hubbell damper-armor-rods-line-protection.pdf Hubbell-suspension-clamps.pdf Hubbell-suspension-assemblies.pdf Hubble yoke plates Transmission connectors .pdf MPS_transmission-catalog-web.pdf  |
 "Unlike ceramics, polymer insulators have relatively shorter life." |
3-phase Transmission Corona ring/ Corona shield "... use of corona ring at the HV (high voltage) end fitting for improving the electric field and potential distributions and then for minimizing the corona discharges'... protecting insulators from corona degradation. 2006 Corona-effects.pdf When polymer insulators are "exposed to intense electric fields, insulation failure and loss of hydrophobicity (water should not be able to penetrate surface of insulator) may occur." "These problems are caused due to non-uniform electric field distribution along the insulator, which tends to intensify the electric field on the sheds nearest to the phase terminal (connection point of conductor and insulator). Non-uniform electric field distribution can be minimized using suitable (correct design, size, and placement) corona rings."  There are "36 different shed profiles for composite insulators. There are four categories for the 36 profiles depending on number of different shed diameters within each unit: .... Category 1.) alternating one large and one small; 2.) one large, two small; 3.) one large, one medium and two small; and 4.) one large, one medium and four small." |
  Larger image3-phase subtransmission Vertical Bundle Suspension on rebuilt Subtransmission line. Bundling Yokes can vary in width, 2-1/2" to 4-1/4" and length 9"-12"-18".  |
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3-phase
transmission Overhead conductors are exposed to wind and other conditions that can damage the wire. To prevent damage, utilities install vibration dampers, armor rods, and in this example, a suspension clamp with helical cushion to absorb movement while protecting the wire. ''Suspension clamp with helical cushion is designed to provide enhanced conductor support and protection. The rubber inserts are assembled directly onto the conductor and are held in place with the helical rods. The clamp assembly is then bolted around the helical wrapped rubber supporting inserts to compete the install.'' |
 Larger image3-phase transmission Steel tower near downtown Houston lays on the ground after being replaced with concrete poles. Image shows two sets of dual porcelain (or toughened glass) strain insulators, each string about 8' long. Note the flexibility of the insulator string, helping absorb the effect of wind on the conductors (hot wires). "A suspension insulator is an insulator which can be assembled with other metal parts and provide the means for non-rigidly supporting electric conductors. Suspension insulator voltage range can be from 10KV to 1000KV, is widely used in transmission and distribution lines. Suspension insulators can be divided into porcelain suspension insulator and silicon rubber suspension insulator according to the material." "Unlike ceramics, polymers have relatively shorter life." Larger image  ",... there are three kinds of materials for suspension insulator: composites with silicone rubber, porcelain or ceramic, and glass." "Polymeric composite insulators consisting of core fiber reinforced polymer insulators covered with polydimethylsiloxane (PDMS) housing are now replacing conventional ceramic insulators especially for high-voltage outdoor (above ground) power transmission lines due to some specific advantages." "Silicone rubber has more advantage over the porcelain, so more and more countries are choosing the silicone rubber suspension insulator vs porcelain" These downed porcelain insulators were replaced with silicone rubber or composite type insulators. Advantages-polymer-vs-ceramic-insulators.pdf "A porcelain insulator consist of a number of porcelain discs connected in series by metal links in the form of a string.'' Each suspension disc is designed for normal voltage rating 11KV Resources: Porcelain-Suspension-and-Struts.pdf Orient-suspension-insulator-definition.pdf Toughened-glass-insulator.pdf 2018 Degradation-and-stability-polymer-insulators.pdf 2006/ polymer-vs-glass-insulator.pdf |
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High
voltage tools Buy: High voltage tools Electrician tools kits Klein tools Tools kits |
 Larger image Stafford Texas  Larger image |
3-phase
Subtransmission The grid generates 3-phase power that is delivered via groups of 3 hot wires that are accompanied by the Neutral. The subtransmission tower pictured is made of steel, making it a natural lightning rod to help protect the grid. The Neutral wire is visible at the top of the steel tower where it is bonded (connected to) the tower and subsequently to the ground. The Neutral, when at top of pole acts as a shield wire to absorb and redirect lightning into the ground via the steel tower. This is called a shielded line and is vital for grounding and grid reliability. The Neutral wire on it's own is important for 3-phase transformer configurations, and for single-phase household and commercial voltages. Across the entire grid, the Neutral is bonded to the ground at each tower, pole, substation, and user location. This forms a giant array of grounding that stabilizes the grid from lightning and overvoltages that can be safely absorbed into the earth to minimize potential damage. Electricity is the flow of electrons from unequally charged materials. Insulating materials including air will stop the flow of electrons until the charge becomes great enough to overcome the insulation. When storm clouds carry a charge, the electrons in the clouds are not equal to the charge on the ground. The result is a buildup of charge to the point where the flow of electrons will pass through the insulating effect of air via a lightning bolt. The lightning will often strike highest point like a tree, house on hilltop, or transmission tower. The shield wire or static wire or system neutral located at the top of transmission and distribution poles and towers is directly bonded to a ground wire, or series of ground wires, at each tower or pole. This ground wire gives the lightning an easy route to earth thus reducing damage caused by lightning. If the lightning carries more voltage than the ground wire can absorb, there can be a flashover onto the power wires, or hot wires. The flashover can cause substation breakers and relays to activate and shut down the line. Suspension insulators hang vertically, but when used horizontally, they are called strain insulators. These types of insulators are used for voltages above 33kV (33,000 volts). Each unit of the insulator is designed for 11 kV. Suspension and strain insulators allow wire to move with wind, and minimize mechanical stresses on the installation to improve longevity. Resource: Porcelain-Suspension-and-Struts.pdf Failure-of-High-Voltage-Porcelain-Insulators.pdf |
 Ball
eye, ball clevis, socket eye,
socket tongue, socket clevis, socket thimble, anchor shackle, twisted
shackle, Anchor shackle, Bow shackle, Chain, and D Shackles, twisted
strap, clevis eye, eye chain link,
chain link, clevis tongue, extension link, U-bolt, adjusting plate,
yoke plate, turnbucklePole-and-Line-Hardware.pdf Suspension clamps .pdf Transmission connectors .pdf Suspension clamp U
bolt type
Strain clampsPreformed armor grip suspension clamp Strain clamp for ACSR, AAAC, steel wire Hydraulic compression type Deadend bolted type |
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 Larger image Rosenberg Texas |
3-phase 22,000-79,000
volt
Subtransmission ... and 3-phase 7200 volt distribution lines Subtransmission and transmission lines travel from substation to substation and are located higher off the ground than local distribution lines. Transmission lines might be 270,000 to 500,000 (270-500 Kv) volts. Subtransmission lines might be 125,00 to 69,000 Volts (125-69Kv). Distribution lines that travel from local substation to each home and business are much lower to the ground and carry less dangerous 7200 volts (7.2 Kv). Note that the commercial three-phase transformer bank in the foreground is connected to the distribution lines, but would never connect to high voltage transmission or subtransmission voltages. Below 4000 volts on in-town distribution line becomes inefficient because high amps cause too much heat loss. Lower voltages can be used on rural lines that serve very few homes. Resource: Design-overhead-distribution.pdf Mechanical design overhead lines pdf Electric-power-distribution-system-operation.pdf |
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3-phase
high voltage Power
transformer at local substation 69K-125K subtransmission lines supply power to local substations. Local substations use power transformers to convert the high voltage subtransmission into 7200 volts for distribution lines that travel to local homes and businesses. The large cylindrical tank mounted on left side contains oil for cooling the transformer. While voltage remain relatively unchanged throughout the day, amperage (or number of electrons flowing along the line) rises and falls depending on the load, with more amps flowing when more loads are turned on. During high consumption periods, or peaks, the voltage is pushing massive numbers of electrons across wires and through the transformers. The increased flow of electrons encounters increasing resistance which acts like friction, causing heat across the whole grid. Transformers are rated by their KVA (power) capacity, and how much heat they can withstand, and how fast they recover (cool) after a high-heat or peak event. Resource Recommended-losses for-power-transformers.pdf Large-Power-Transformers-and-the-Grid.pdf |
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3-phase distribution Many poles leave substation transformers, traveling to each business and neighborhood Wires leaving a local substation branch off many directions on many wooden poles, sending power all directions. This is the source of 7200 volt distribution. Distribution lines can travel many miles from substation to local towns, or substation can be located near town, or near neighborhoods etc. Follow power lines using google earth to reveal complexity of transmission and distribution networks. Poles leaving substation carry groups of 3-wires, always accompanied by Neutral. Poles are generally wood, but can be steel or concrete. Each pole has ground wire running down pole and into the ground |
 Larger imageNewly installed 3-phase 7200 volt distribution lines Air is the insulation. This newly installed overhead distribution line is made of 7/8" diameter bare aluminum-alloy wire. Overhead wires are bare and have no insulation. Wooden poles have good insulating properties, and generally last 25 years before they are rotted beneath the ground and need replacement. To ensure power does not arc to ground or other structures, high voltage wires are suspended in the air, using the air as insulator. The higher the voltage, the higher the wires are suspended to ensure safety. The pin type insulators on each pole keep bare wires away from poles and other wires. Insulators must have high mechanical strength to withstand loads such as wind and have high electrical resistance. 'Porcelain is most common material for insulators, but glass, steatite and other composite materials are used. Pin type insulators are used up to 11 kV (11,000 volts)' 'Bare overhead wires are cheaper to install but don't last as long as insulated underground cables. Underground transformer vaults can be susceptible to flooding and water damage. "Overhead line construction is less expensive than underground cabling for the same kVA (power) load. In rural or semi-rural areas, the sheer cost of underground cabling would make it impossible for customers to afford cost of supply. The downside is that overhead lines operate under continual mechanical stress with exposure to varying climatic conditions (wind, heat, ice, lightning etc). This results in progressive deterioration in time as a result of corrosion, mechanical wear and fatigue, timber rot, etc. All components must be periodically inspected and replaced" "Overhead systems are rarely as reliable as underground ones. The greater spacing of overhead line conductors generally results in higher system inductance (resistance) than for a cable system. This means an overhead line has a greater voltage drop than an underground cable of equal current-carrying capacity and hence cannot supply power over as long a distance as the underground equivalent. However the capacity of an overhead feeder can be readily increased by replacing it with larger conductors and/or increasing the voltage insulation/operating level. This flexibility is one big advantage of overhead systems." Source P18 |
 Larger image Full image Power plant switchyard to 3-phase 500,000 volt Transmission to 3-phase 69,000 volt Subtransmission to 3-phase 7200 volt Distribution to single phase 7200 volt Distribution to single-phase 120-240 volt Home Power plant to house electricity Illustration shows grid transmission from power plant to substation, subtransmission from substation to substation, and distribution from local substation local homes and businesses. Homes and businesses require high-amp, low-volt power. Except high amperage causes heat loss during long-distance transmission. To solve the problem, transformers located at substations can raise and lower amps by raising and lowering voltage. Voltage and amperage are inversely proportional. Volts x amps = watts. When volts are reduced at at substation transformer, amps are increased. The result is low-amp 500,000 volt electricity is used for long-distance transmission. Higher amp, 69,000 volt subtransmission lines are used for shorter distances. And higher amp 7,200 volt is used for local distribution lines. For example, transformers at local substation reduce 69,000 volt subtransmission lines into safer 7200 volts so it can be distributed along wires that are suspended nearer to ground and can pass close to trees. Residential single phase is achieved by taking one 7200 volt Hot wire and a Neutral off the 3-phase 7200 volt distribution line to create 7200 volt single phase. The 7200 volt Hot and Neutral are then connected to each of the residential transformers in the same neighborhood. Converting 7200 volt 3-phase into 7200 volt single phase ... pulling 1 Hot and a Neutral off 3-phase distribution line. Once the 7200 volt Hot and Neutral wire reach each home, the residential transformer will reduce the 7200 volt single phase into usable 120-240 volt single phase, ensuring that households receive safe, low volt, high amp power.  Numerous homes will draw amperage off the same 7200 volt power line without overtaxing the line. That's because a 250 amp 120-240 volt residential service that is running at full capacity will pull a maximum 8 amps off the 7200 volt distribution line. At any given time, very few home will be running at maximum amperage. Most will draw just a couple amps off the 7200 volt power line. Resources See calculation Ampacities of power lines Larger image Low volt, high-amp power works nicely because household 120-240 volt single-phase can be safely controlled by small switches, relays, cell phone chargers etc contained within steel and plastic enclosures, while the amperage (and heat) is controlled by circuit breakers (overcurrent protection) and then distributed to outlets, switches, clothes dryer etc using correctly sized wire to match amp rating of breaker. Resources: What is 3-phase See inside residential main breaker box Basic household electric Troubleshoot household electric Generally, in the US, each home has a transformer that converts 7200 volt Hot and Neutral into split phase 120-240 volt service. Sometimes more than 1 home will share a transformer... result is dimmed lights, or voltage drop each time heavy equipment such as HVAC turns on. Resources: Identify transformer wiring Difference between single-phase and 3-phase |
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 Larger imageGrounding 3-phase distributin "Standard 142-1991 lists several reasons for limiting the ground fault current by resistance grounding: 1. To reduce burning and melting effects in faulted electrical equipment, such as switchgear,transformers, cables, and rotating To reduce burning and melting effects in faulted electrical equipment, such as switchgear, transformers, cables, and rotating machines. 2. To reduce mechanical stresses in circuits and apparatus carrying fault currents. 3. To reduce electrical-shock hazard to personnel caused by stray ground fault currents in the ground return path. 4. To reduce the arc blast or flash hazard to personnel who may have accidentally caused or who happen to be in close proximity to the ground fault. 5. To reduce the momentary line voltage dip occasioned by the occurrence and clearing of a ground fault. 6. To secure control of transient over-voltages while at the same time avoiding the shutdown of a faulty circuit on the occurrence of the first ground fault (high-resistance grounding)." By Larry A. Pryor, P.E., GE Senior Specification Engineer. "... lightning activity can be characterized by lightning ground flash density, expressed in terms of number of lightning flashes to ground per square mile per year. The line itself tends to be a somewhat focused collector of lightning and will attract flashes which would otherwise strike the ground over a swath whose width is approximately four times the average height of the uppermost conductor or shield wire" ... the Neutral or static wire found atop transmission, subtransmission, and distribution poles. If a pole has the 3 Hot wires at the top and Neutral traveling lower on pole, then the line is considered unshielded from lightning. In this case "lightning to unshielded lines involves a strike to one of the phase conductors (hot wires), resulting in line outage. "For properly designed lines, having well located shield wires (as shown in photo), most lightning strikes to the line will terminate on the shield wire. The surge of current will travel along the shield wire until it reaches a structure (pole) where it will be conducted down into the ground'" Transmission surge arrestors .pdf |
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3-phase and Single-phase 7200 volt distribution Typical 3-phase distribution line follows alongside a road or street, and supplies both 3-phase and single-phase for all end users located along the road or street. Three phase distribution line has 3 out-of-phase Hot wires accompanied by the Neutral. Normally, a 3-phase service has 3 transformers, and takes 3 Hot wires and sometimes the Neutral, while single-phase service has 1 transformer, requiring 1 Hot and the Neutral. The same distribution line can supply power to multiple neighborhoods with each neighborhood pulling off a separate Hot wire in effort to keep the 3-wire 3-phase distribution lines 'balanced.' Balanced mean all 3 hot wires on the 3-phase distribution line will supply the same amount of power, and that one hot wire does not do more work than other two hot wires. |
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7200
volt distribution Hot clamps are used to connect distribution lines to transformers at each home and business. Hot clamps are also used to pull a 7200 volt distribution line off the three phase distribution to supply single phase to a neighborhood. This type clamp is used on 7200 volt distribution lines, but never on high-voltage transmission and subtransmission lines. Resource: Line post-insulator.pdf Hot clamps pdf |
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Single-phase
7200
volt distribution Hot clamps For connecting transformers and other wires to a 7200 volt distribution line Resource: Hot clamps pdf  |
 See Larger Neutral connects to transformer. Ground wire connects to Neutral wire. Ground wire is smaller diameter than Neutral. Ground and Neutral work together for household safety, stability of grid, and to help absorb overvoltages and shorts caused by lightning, equipment failure, surges from inductive loads etc. |
Single-phase 7200
volt distribution line arrives at home Power poles carry high-volt, low-amp electricity -High-volt low-amp lets power company transmit electricity long-distance without heat loss caused by high amperage. Before entering house, electricity is converted to lower volts and higher amps at distribution transformer. Different transformers are used for different voltages. -Residential transformers receive 4500-7200 volts from 1 high voltage line and a neutral. The transformer reduces voltage to 240Volts and splits the voltage into two 'out-of-phase' 120Volt Hot wires that enter home. The two out of phase Hot wires offer 240Volt potential used to power water heaters, air conditioner etc. While 120 volts using 1 Hot and 1 Neutrals used for outlets and lights. -Note: 3 wires enter home <> 2 hot wires and 1 neutral wire <> the neutral also connects to ground wire at bottom of service pole. The ground wire is bonded (connected) to the ground rod that is driven into the soil and is used for safety and to stabilize the grid. Resources: Where power comes from: What is 3 phase Difference between household and commercial electricity Read about electric power from power plant Why you need ground wire |
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Single-phase
7200 volt distribution line arrives at home Underground residential electric service is same as above-ground service -It's easier to photograph above-ground electric service. -All electric services, above and below ground, follow same pattern from power line => to transformer => to meter box => through the meter => to main breaker box. -Meter and meter box for underground service is the same as above ground, except wires arrive in underground conduit pipe instead of dropping down from a pole. -Transformers for underground service are inside ground-level boxes or underground vaults, and perform exactly same function as above- ground, except offer more protection, reliability and longer lifespan. Resource: Underground electrical vaults .pdf |
 Larger imageSingle-phase 7200 volt distribution line arrives at home 7200 volt Hot and Neutral wire arrive at home. The Neutral is at top of pole, and Hot wire is suspended lower on pole. The residential transformer converts 7200 volt distribution line into safe 120-240 volt for use inside household. This transformer supplies power to a single home. Power is pulled off the Hot line using a Hot Clamp attached to the Hot line. The fuse protects against overloads and fault currents (amperage). The surge arrestor protects against overvoltage. Both work together to protect the installation. 'Transformers have no moving parts, ensuring a long trouble-free life under normal conditions.' Power leaves the transformer via triplex wire that is attached to side of transformer. Triplex is a 3-wire bundle made up of two insulated Hot wires and a grounded bare aluminum neutral wire that are strong enough to be suspended overhead until they enter a service mast and drop down into the meter box before entering the household main breaker box.
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 Larger imageSingle-phase 7200 volt distribution line arrives at home Same as above: 7200 volt Hot and Neutral wire arrive at home. The Neutral is at top of pole, and Hot wire is suspended lower on pole. The Neutral atop the pole serves as a shield wire to catch lightning strikes and safely redirect the excess voltage to ground so it will not damage the electric grid. High-strength steel wire for long spans that carry few amps. Resources Overhead grounding standards Grounding code Dead end clamps  Larger image |
 Fuse Full image |
 Tripped or open fuse Larger image |
Single-phase 7200 volt
distribution
line Fuse cutout located on power pole -High voltage distribution wires carry 4500-7200 volt that must pass through a fuse before connecting to transformer. -Fuse will trip when heat exceeds fuse rating, protecting transformer from surge caused by lightning, overload, malfunctions etc. -Electric company resets fuse using long fiberglass pole. -Far left image shows high voltage line terminating on a porcelain dead end strain insulator located on last pole at end of street. Resource cutout-fuse-instructions.pdf |
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7200
volt
distribution
line Dropout fuse ''The primary function of the drop out expulsion type fuse is to protect equipment connected to distribution overhead lines from overloads and fault currents within its rating.'' This type fuse is used on 7200 volt distribution lines, but never on high-voltage transmission and subtransmission lines. Resources Cutout-fuse-instructions.pdf Hot sticks and power line tools pdf Fiberglass Hot sticks arc-flash-clothing.pdf power-line-tools.pdf  Lineman resets fuse at night Larger image |
| Static belt
serves as continuous ground/ protection
when
working close to energized lines Conductive suit, hot suit, conductive Boots, socks, gloves / clothing is bonded to the conductor so lineman can use hands on live conductor Rubber insulating gloves must operate within voltage class, must be in good condition for work on hot lines Protective Ground Grid / ground blanket/ for a lineworker to stand on during energized and de-energized work Temporary conductor support fiberglass is used to hold energized distribution conductors during replacement of poles or repair or replacement of pole top and stand-off insulators Temporary Conductor Support: Nylon binder strap ratchet assembly hold energized distribution conductors during replacement of poles or repair Grounding set with grounding clamp each end Resources Hubbell Performed energy Spun concrete poles Lineman slang dictionary Performance-Evaluation-Overhead-Power-Line-Proximity-Warning-Devices pdf Aerial-tools-and-equipment.pdf Distribution repair manual |
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Single-phase 120-240
volt residential service Resource: See inside household electricity  Larger image Single-phase distribution transformer -After 7200 volt distribution Hot wire travels through the fuse, it drops down to the lightning or surge arrestor, and then connects to the primary bushings located top of the transformer. Note the Neutral wire connects the other bushing on top of transformer, and also connects to ground wire. -The ground wire is bonded to the shell of the transformer, and to any metal that is attached to pole before traveling down length of pole into soil at base. Across the grid, all poles, transformers, and electrical services are grounded, with all grounds bonded to the Neutral, forming a giant array of grounding that stabilizes the grid against overvoltages, lightning and insulation failures etc. -The transformer photo shown above supplies electric service to two homes instead of more typical single home. Disadvantage of serving two homes is lights flicker when heavy amp loads turn on, such as air conditioner. -Electricity leaves the transformer and travels through 3-wire bundles called triplex that contains 2 Hots and 1 Neutral. |
 Why are transformers used?"Three-phase transformer banks are used in three-phase AC power circuits for the same reasons as single-phase power transformers in single-phase ac circuits, i.e., to step-up or step-down the voltages in the circuit and to provide electrical isolation (separation) between the primary windings (coils) and the secondary windings." Transmission and distribution lines from the power plant are high voltage, low amperage to reduce heat loss. Heat occurs when voltage pushes amperage (current of electrons) against the matrix, or atomic structure, of the conductor. Using high voltage and low amperage means more force is pushing fewer electrons against the conductor matrix, which means less resistance from the conductor and less heat. Resource Ampacities of power lines By reducing heat loss, electricity can be transmitted longer distance without losing power. To prevent electricity from jumping (arcing) to other wires, or to the transmission tower, or to the earth, high voltage conductors (wires) are suspended high above the ground and spaced far apart, utilizing air as an insulator. The higher the voltage, the more space is needed to keep the voltage under control. High voltage also requires large and expensive switchgear, and is extremely dangerous, making it impractical and hazardous for residential and commercial use. To solve the problem, transformers are used throughout the grid to step up or step down voltage. Since amps and volts are inversely proportional, when volts are stepped down by the transformer at local home or business, amps are stepped up. The lower voltage can be controlled at home and business using small switches contained inside metal or plastic enclosures while amps are controlled with properly sized circuit breaker and wire. |
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3-phase
arrives at building 3-phase 7200 volt distribution line arrives at commercial building Typical 3-phase service has 3 transformers, while single-phase service has 1 transformer. The same distribution lines that supply 7200 volt to neighborhoods and individual homes also supply power to businesses and buildings that require 3-phase service. Single phase power delivered to homes requires one transformer, while a 3-phase service to buildings requires 3 transformers (which are sometimes installed as a single transformer that contains 3 transformers). A service is the voltage and amount of KVa or power that is delivered from the grid to the building. A residential service is 120-240 volt single-phase, while a commercial 3-phase service can be a variety of voltages including 120-208-240-277-480-347-600 volt etc. ''When a building is not of sufficient height, a service riser will be necessary to achieve the proper service drop clearance. When field conditions do not permit the use of a riser, a service pole may be substituted.'' Resources JEA-Overhead-Grounding.pdf Difference between single-phase and 3-phase What is 208 volt What is 277 volt |
 3-phase 7200
volt
distribution
lines arrive at building service
Original image Rosenberg Texas 3 phase service at local Walgreen Image shows Delta Primary and 4-wire WYE Secondary. The primary is Delta: How do we know? Each 7200 volt hot wire from the distribution line connects to two different transformers.... so the three transformers are wired in series or Delta on the primary (or distribution side). The System neutral connects to Neutral and ground, but not to the bushings on top of transformers. The secondary is WYE. There are 4 wires, 3 hots and 1 Neutral. The Neutral connects to all three transformers. Each of the 3 Hot wires connect to a different transformer ... so the three transformers are wired in parallel or WYE on the secondary (or customer side). Delta primary, WYE secondary is 'most common type of wiring' because Delta has lower amps/ meaning less heat, so insulation on primary coil on each transformer is less expensive. Transformers can be wired different ways depending on the incoming electric supply and end user need. Two key factors for the grid are economic performance and reliability. Reliability is necessary because electricity must run clean without high-voltage spikes and low-voltage brownouts. Unreliable power means motors and HVAC equipment will have shorter lifespan. Resources: Transformer configurations pdf Index of transformer manuals Identify more illustrations of transformer wirings Power line surge protectors pdf Read more about 3-phase service |
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 Larger image Rosenberg Texas near fairgrounds |
3-phase
7200
volt
distribution
lines arrive at service 3 phase service at county fuel depot With 3-phase service, there are several different standard voltages and transformer configurations depending on end user need. In this case, the 3 transformers on Primary side are connected in parallel (WYE) since the Neutral wire connects to the Neutral bushing on each transformer. Likewise, the Secondary or customer side is wired in parallel, so this is a 208-120 volt, 480-277 or 600-347 volt WYE-WYE service. Note that the Neutral wire is below the 3 Hot wires. This means the Neutral cannot function as a shield against lightning strike. Since the location had no other tall structures nearby, an unshielded service is more prone to damage since lightning will energize the Hot wire(s), causing potential outage and damage. The fuses and lightning arrestor located on each Hot line and transformer will minimize damage. Resources: What is 3-phase |
 Larger image3-phase 7200 volt distribution lines arrive at building service High leg delta service at local business 7200 volt distribution power comes from across the street on 3 Hot lines and 1 Neutral The Neutral can be at the top if there is higher risk of lightning. The Neutral will redirect a lightning strike into the ground wire at each pole. Otherwise, the Neutral is installed below the Hot lines as shown in Fig-2. If lightning or surge impacts the Hot wires, the lightning arrestor and fuse will protect transformers. If surge on the Hot wires exceeds rating of wire and grounding, the breaker at substation will trip and protect the distribution and transmission systems. While wires on the secondary side going to the customer service panel are always insulated, the distribution Hot wires in this picture are bare, stranded aluminum or aluminum alloy, approximately .8-.9" in diameter. Wire size and material used for the grid are a balance of cost and performance. For example, copper offers less resistance and less expansion and contraction than aluminum ... and steel is very strong and resistant to heat ... but aluminum and aluminum alloys are the choice for most overhead electrical conductors. Copper is best choice for interior wiring inside business and home. Inside home or business, aluminum wire will expand and connections come loose with high-amp loads, creating high risk of fire unless properly installed with special AL-rated compression fittings. Resources: Types of electric cable pdf What is high leg delta |
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 Rosenberg Texas near fairgrounds |
3 phase service drop The image in table above shows the primary and transformers The image to left shows the service drop for the image above. |
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Same service drop as the
image above. Resource: Drop-wire service ends |
| http://waterheatertimer.org/pdf/Drop-wire-service-ends.pdf | |
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leaving service pole and transformers, 3-4 insulated wires drop down to
commercial building.To avoid contact with trucks, people etc, a service drop must meet standards for height above ground. This service drop has a riser to meet height requirements. The power enters each service mast via insulated wires that enter the weatherhead and travel to the meter first, and then though a service cut-off, before entering building. Each business served by this installation has a separate meter, and each metered line must have an easily accessible safety cut off or safety switch with pull-down handle to de-energize power in case of emergency, repairs etc. The steel riser, weatherheads, conduit, meter boxes, safety switches etc are grounded for safety. |
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 Larger image Overhead switch/ Sectionalizer 3-phase 7200 volt distribution lines >"Sectionalizers are one of the most used for distribution system protection. The sectionalizer opens and isolates the faulty section of line. This permits the power company to re-establish supply to those areas free of faults. If the fault is temporary, the operating mechanism of the sectionalizer is reset." Overhead switch lets power company de-energize lines for repair and emergency A metal pole with a manual switch lever is located at bottom of pole When switch is open the line on one side or the other is de-energized. Resource: 4 Factors To Consider When Selecting a Sectionalizer |
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Overhead switch/ SectionalizerLarger image >Rosenberg Texas |
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Overhead switch/ SectionalizerLarger image Rosenberg Texas |
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| http://waterheatertimer.org/Pulling-electric-wire.html | |
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More overhead wiring Resources: Sectionalizer Hoist stick pdf Jumpers etc pdf Jumper clamps pdf Line construction tools Web ratchet puller pdf Pulling-electric-wire What-is-3-phase-electric |
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Compression
Splices After wires are pulled together by tensioner, a compression splice or sleeve is added to securely connect both sections of wire. The conductor is cleaned and inhibitor applied to both surfaces, and then spliced is applied. Resource: Hubbell-splices-and-sleeves.pdf Splice repair Splices-en.pdf Inhibitor .pdf |
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Lineman's utility cart carries rolls of smaller wire
used for neutral,
grounding and guy wires, and triplex drop wire for residential service. Each lineman is trained for specific voltage range because protective equipment, parts, materials, safety-equipment and other factors vary by voltage. |
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Fig-A shows freshly cut 37
strand 'concentric round' aluminum bare overhead Distribution
conductor with strands
of wire splayed apart. Fig-A is called
'concentric round' since each
strand is identical, each is round, and cable is round. Diameter 0.795."
This wire was laying on the ground as part of the installation of new Distribution lines along the freeway. Note: "each layer in a conductor is wound in the opposite direction" Fig-B shows 28 strand bare overhead Subtransmission conductor with 7 strands of high strength steel surrounded by 21 strands of trapezoidal-shaped aluminum wire. ''Air space between
strands can be reduced by compacting the aluminum
conductor into
trapezoidal shape for a more compact wire size."
Wire in Fig-B was laying on the ground as part of the installation of new Subtransmission lines along a local highway. "Overhead wire can have 70-127 strands and be 2.3" or more in diameter, and made from a variety of aluminum alloys. 12mm˛ to 750 mm˛." Household wire can be 7-19 strands and less than 1/4" across Zinc coated and aluminum coated steel wire are used where temperatures exceed 200° F. Resource pdf: Ampacities-of-overhead-conductor Amp-rating-power-lines.pdf Overhead-Installation-Guide 4_overhead_conductors Mechanical-Design-of-Overhead-Lines Advanced-Conductors-for-Overhead-Transmission Design-overhead-distribution Overhead Conductor Installation .pdf Overhead-aluminum-conductor |
 Larger imageSize comparison steel core 28-strand trapezoidal Subtransmission wire and 37-strand concentric round aluminum Distribution wire. Trapezoid design eliminates much of the air space between strands, allowing higher-voltage wires to have more compact diameter. Each layer in a conductor is wound the opposite direction  |
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Conductor
examples Different conductors are chosen for different applications Illustration is general depiction of materials and not exact numbers of strands or types of cores or shapes of wire configuration.  Choice
of conductor is always a balance of electrical need, efficiency and
cost of materialsGalvanized steel wire surrounded by aluminum wire is used for long spans. ACSR ACAR Steel wire is strong, but a poor conductor. The aluminum wire carries most of the electricity. The 'skin effect' causes most of the current to flow close to the surface of the wire For shorter spans, up to 50 meters, with high load demand, all-aluminum wire is used. AAC AAAC For rural areas with few customers, price of conductor becomes main issue. Galvanized wire is used. Galvanized steel is a poor choice of conductor for areas with high load Overhead conductors can last at least 40 years Resources: Overhead conductors pdf Amp rating of power lines Ampacities-of-overhead-conductor.pdf Utility-Wire-and-Cable.pdf Overhead-wire-types.pdf Wire types pdf Overhead aluminum conductors General cable/ overhead conductors ]General cable/ overhead line solutions |
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Formed Wire:
Deadends for Guy Wires, laying on ground next to 7/8" diameter distribution conductor (wire). In lineman slang, wire ties are called wiggle wires. Wire ties are used to attach the conductor to the insulator at each pole, and attach guy wire to anchor etc. Wire ties are prefabricated for each wire size When viewing electric repair trucks and supply trailers on the road, you can see the pre-fabricated ties hanging on back of vehicle Resource pdfs Lineman slang Hubble Brenco General Cable Formed-wire |
 Resource: Spun-Concrete-Poles-Valmont-Utility.pdf For subtransmission and distribution |
 RCC reinforced concrete pole/ High-voltage Subtransmission tower/ with local distribution lines running lower on pole Vertical bundling for twin conductor suspension, Vertical Bundle Assembly Suspension Clamps Rosenberg Texas |
 Distribution line Larger image Rosenberg Texas |
3-phase 7200
volt
distribution
lines Hot from North side of freeway attaches to South side Suspension clamp is tightened against wire using 4 bolts. Wire is bent downward. The bend in wire adds a mechanical resistance to slippage of wire The bend also pulls the Hot wire away from the insulator. The Hot wire is connected to Hot wire on pole. Suspension clamp is connected to insulator. Insulator is bolted to steel pole Long suspension spans use aluminum-coated steel wire or steel cored aluminum ACSR Aluminum wire will sag more than steel wire over long spans. Steel coated aluminum wire is used. The steel carries mechanical strength while aluminum strands carry bulk of current Poor conductivity of steel makes it a poor choice for long distance transmission of high voltage. Galvanized steel is used in rural areas with few customers on the line because it is less expensive. Resources: Spun concrete poles Spun-Concrete-Poles-Valmont-Utility.pdf prestressed-concrete-poles.pdf Dead end clamps pdf |
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Compression hot clamp Color difference
added for clarity
Distribution
hot line connected to another
distribution hot line.Used for higher amperage application compared with hot clamp used for home. Wires shown are 3/4" diameter, 37 strand aluminum Resource: Overhead-primary-clamps.pdf |
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Hot
clamps For connecting wire to distribution line Resource: Hot clamps pdf |
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7900 volt distribution Suspension clamp and silicone strain insulator Suspension clamp has 4 bolts that are tightened against wire. The clamp holds wire and keeps it from slipping. Used when suspending wire across long distance or at pole located at corner Strain insulator vrs suspension insulator Resources: Mechanical design overhead lines Transmission power pole parts.pdf Overhead-primary-clamps.pdf Dead end clamps pdf Suspension jumper support |
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7900 volt distribution Strain clamp and silicone strain insulator This lighter-weight version of assembly shown above. Power company installed new poles for freeway construction When new poles were wired and energized, the old poles were taken down. Hardware was removed from old poles. This assembly was left along freeway .... I picked it up from the ditch, photographed it following day, and returned it to the ditch. Surprising was that the fins on the insulator were rubber (silicone) material, as was the coating around the insulator. The fins are for dissipating heat |
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220,000-240,000 volt Transmission assembly Resource: Hubbell-Power-Systems-Deadend.pdf |
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Subtransmission
installation Quadrant Strain Clamp Deadends  Resource: Hubbell-strain-clamp.pdf Anderson-dead-end-clamps.pdf |
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230,000-324,000 volt Transmission
assembly (Insulator shortened for illustration) |
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Strain
clamp and porcelain strain insulator This older installation used porcelain strain insulators and wood pole. The function was to bring 3 Hot wires and a neutral across the freeway and connect onto the 3-phase distribution line that runs parallel to freeway. The pole and wiring were updated when new freeway construction required poles pushed back farther away from road. The wood pole was replaced with a 26,000 lb spun concrete pole, all new wire and hardware installed and the porcelain strain insulators were replaced with new style silicon insulators. Pin type porcelain insulators were still used with the new installation. Resource: Hubbell-Tee-and-jumper.pdf Hubbell-dead-end-strain clamps.pdf Anderson-dead-end-clamps.pdf   |
 Larger image Rosenberg Texas |
3-phase 7200
volt
distribution
lines Neutral connection at top of pole :Neutral from pole north of freeway, tied to Neutral line on south pole using 2 compression fittings Neutral connected to top cap insulator using side tie Compression or crimp connection is accomplished with hand tool that looks similar to bolt cutter Resource: Grounding steel poles |
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Aluminum distribution clamp Before installation, both conductors are cleaned with wire brush and coated with inhibitor Resource: Crimping tool pdf Cutters pdf |
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Distribution pole assembled on ground Poles are delivered without hardware, and dropped in location where each will be set. Linemen install hardware that is assembled to specification. For example the polymer riser (insulator) must be set at specific distance from bottom of pole, and from each other etc. Wood poles are used for spans up to 50 meters. Wood poles rot underground after 20-25 years Cannot be used for voltages higher than 20 Kv Resource: Mechanical design of overhead power |
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Power pole tool: Cant Hook Linemen use ordinary tools: drill, wrench, stapler They also use specialized tools such as the tool shown (cant hook) that is made specifically to roll the pole, or keep it from rolling. They use climbing spikes and safety belt when ascending and descending pole. |
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Cant Hook |
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Distribution pole assembled on ground |
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Top of power pole A shackle insulator has been added to pole. This is a type of strain insulator that lets linemen install a short line to another pole for local service |
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Standoff for neutral wire that will drop down to the
transformer, or to the ground wire. Extra length of neutral wire looped back in toward the pole will be attached to Neutral wire at top of pole. Shackle or spool insulators can be made of ceramic, glass, polymers etc and are used to hold the triplex drop line going to a home. The fiberglass guy strain insulator is attached to pole at one end and guy wire at other end. The purpose is to insulate the guy wire from any possible contact with live voltage from the pole. Resource: Guy strain insulator .pdf |
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Standoff for neutral wire Each wooden pole on the distribution grid has a Neutral-ground wire that travels down the side of pole. Standoffs are used to keep the neutral wire away from hot wires ... And help prevent possible arcing from the hot to metal parts on the pole and then to ground. Once the neutral is below the height of the hot wires, the ground wire is attached directly to pole. The neutral also connects to Neutral going to business or home At the transformer, a ground wire is connected to neutral and to each transformer Bottom of pole, the ground wire enters the soil at a depth specified by local code to meet proper ground for the type of soil conditions Resources: 3-phase electric Household electric service Why you need ground Formulas-for-Ohms-law |
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Standoff for Neutral wire with Neutral wire attached Extra wire will be connected to Neutral wire at top of pole |
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Neutral compression connection found where neutral
wires are connected together at top of pole, or connected to ground
wire. Hand crimped connection using crimp tool, Every pole has a Neutral-ground wire. The ground wire going into the soil at base of each pole always connects to Neutral The Neutral wire runs down side of pole to the soil when a ground connection is made Each ground is connection is determined by type-of-power plus location, type of soil etc Neutral wire runs from pole to pole across the entire grid. Ground wire is connected to each neutral across the grid to stabilize and protect grid from overvoltages, surge etc. Before installation, both conductors are cleaned with wire brush and coated with inhibitor |
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Copper ground wire at bottom of power pole: Butt coil Depth of pole into ground is determined by engineers during planning stage Once the pole is set in the soil, the weight of pole helps the ground make contact with soil Using a coil of wire on the the bottom or butt of the pole is common technique. Using a butt plate is another method. A butt coil is made from the #6 copper wire that is stapled to side of pole. The copper wire is coiled on the bottom, and pieces cross each other to maximize contact. In addition to the coil, a ground rod is also driven into the soil to depth that is specified by engineer. Depth of ground rod is based on resistivity and dampness of soil. The ground must reach soil that is permanently damp... and below the frost line This installation is done in a damp Texas coastal region with clay soil. Dense soil such as clay has less resistance to ground than dry rocky soil. The best soils are dense, non-frozen, clay. The worse soils are loosely compacted gravel with a permafrost. Grounding specifications vary by soil, type of pole, voltage, etc. Resource: Why you need ground Overhead grounding standards pdf |
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Ground wire, ground rod, butt coil, guy wires etc are pre-installed on pole before pole is set in hole. |
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Neutral wire runs full length of pole to the point
where the ground wire connects. Here is the connection point between the copper ground wire and the aluminum-coated steel wire that runs to top of pole On some poles, the copper wire is used for full length of ground. In this instance, the aluminum-coated steel or aluminum wire is used since it is cheaper. The bare copper wire is #4. Copper can never be installed above the aluminum to prevent copper salts from washing down on aluminum. |
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The Neutral wire on each pole or tower, no matter if
pole is wood, steel or concrete, or used for transmission,
subtransmission or distribution, is bonded (connected) to a ground
(earthing) located at bottom of pole. The massive array of grounding protects the grid from overvoltages, lightning strikes etc and carries throughout the grid, all connected together by the Neutral wire continuously from power plant to end user. |
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Guy strain insulator connects to pole. Guy wires cannot be energized with electricity. To solve problem, guy strain insulators are attached to pole at one end and then attached to guy wire lower down. The guy wire is then attached to anchor that is driven into ground. Resources Performed-Guy-Strain-catalog.pdf Preformed_Guy_Strain_Insulator.pdf |
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Guy
wire anchor The load resistance of an anchor is based on soil conditions. Resource: Hubbell anchors |
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Assembly of parts before installing guy wire for new
pole Resource: Guy markers |
 Larger imageTripleyeŽ Guy Adapter with a Pulling Eye is made for attaching 3 guy wires to a single anchor. Other guy adapters are made for 1 or 2 guy wires. Load capacities vary by type of soil and are determined by installation torque. Each guy wire has a Guy Grip that wraps around the guy wire and attaches it to the guy anchor. Guy wires do not carry voltage and are safe as long as attached to the guy anchor. In Houston, a boy was electrocuted when a loose guy wire was being used as a 'grapevine' for swinging back and forth. Guy wire came into contact with live power up at the transformer. Guy markers are important for safety. Without the yellow guy marker, it would be easy to walk into a guy wire and trip or injure oneself easily. Resource: Hubbell anchors Hubbell anchor tools Guy grips |
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Steel guy wire is stronger and less expensive than alternative metals |
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Guy
wire ''Down guy travels downward at angle and is attached to guy wire made of 7-strand galvanized wire. Diameter of wire and number of guys vary by load requirement. The guy wire is attached to the anchor. Parts include the lead section, and extensions. The anchor lead section and extension are screwed into the soil to the correct depth based on soil and load. A soil probe is used test the soil, and results compared with charts that give correct soil classification. Extensions are used to increase depth. The guy wire connects to an extension which is connected to the anchor. The entire guy assembly is connected together and to the pole using hardware such as anchor rods, thimble eye, couplings, eyebolt, eyenuts, shakel, clevis, wrap guy, guy lock, guy grip. The down guy is covered with a shield at the bottom, called a guy marker. The purpose is to make guy wires visible to the eye and avoid collisions and encounters with people, animals etc that might get hurt or damage the guy.'' Resources: Guy markers Guy anchors Aluminum conduit standoff Deadend-guy-en.pdf |
| Connect electric wire to insulator | |
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Top cap Top cap is one type of insulator used to keep wire away from pole. Wire can be attached to top of cap, or on side Top cap is type of insulator used to keep wire from touching the pole Insulators are required to withstand mechanical and electrical stress. Electrical stress is caused by line voltage... failure is caused by a crack or puncture and flashover. Higher voltage/ the greater the cost of insulator Over 33Kv, a suspension insulator is used instead of a pin type insulator Resource: Mechanical design of overhead power |
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Preformed Tension Clamp Preformed Wraplock Tie Top cap and side tie Top cap sitting on disturbed soil near freeway construction. Prefabricated tie partially om the cap Tie has rubber insulator to hold wire away from insulator |
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Wire, side tie, top cap. Same image as above, photoshopped. with photo of Neutral wire |
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Simulation of connection using photoshop. The tie wire is wrapped 1 turn around cap Rubber insulator on side tie forms a barrier between wire and cap Tie is twisted around the wire.  |
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Connection at top of pin insulator Resource: Preformed Wraplock tie Types-of-insulators.pdf  |
| Pulling new subtransmission wire | |
 Larger imagePulling new subtransmission wire requires specific size sheaves depending on size of wire etc. The power company set this metal crate at base of each pole. Each sheave has 3 separate wheels so power company can run 1,2 or 3 wires. See image Next they raised each sheave, one at time, up to the correct height where two men in a bucket truck attached the sheaves to the 3 line post insulators. |
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Line post insulator is
made from hydrophobic silicone polymer, or silicone rubber compound. Bottom Fitting is an aluminum Gain Base. The live end fitting on this one is called a Tear Drop Blade. Other types include Horizontal Clamptop. Source Hubbell The power line was designed for two conductors (wires). Each wire was pulled separately. Resource: Line-post-Insulators.pdf |
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There are 3 large spools of wire at one end of the pull
that are
held in a machine called a tensioner, and at other end is a machine
called a puller. First they run 3 steel cables from the puller that is strung through each sheave and goes to the tensioner. The 3 pull cables are attached to the 3 conductors at the tensioner. See image The puller pulls the wire through the sheaves to the end point, while the tensioner reels out the cable, ensuring the wire is not pulled so hard that it splays apart the strands. The wire must maintain it's structural shape and design to function correctly. Damaged wire can overheat, causing inefficiency and point of failure. Double String Dead End Polymer Assembly  |
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 Contactors/ relays |
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