Rural Electrification Systems
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FORWARD: This page is being ported from the MICROFICHE REFERENCE LIBRARY. This is not an exact port of the original document and is currently a work in progress. The following content was designed by the Volunteers in Technical Assistance and was used as a project of Volunteers in Asia. This group is apparently no longer existent and this file is now out of print. The excerpts of this text will help in the construction of a rural electrical system.
[edit] OVERVIEW
The purpose of Electrification is to provide power to do work. This work my be running a Pump, lighting a house, or numerous other jobs. Controlled Power is very important in all our lives. Uncontrolled power can be very dangerous. The electrical worker must understand the basic principles of electricity, and how to control electrical power. If he does not have this knowledge he will be handling uncontrolled power, at the risk of life, property, or wasted power.
[edit] BACKGROUND ESSENTIALS
These are all key words or terms that anyone proceeding through this work should be familliar with:
Electrical circuit, Ohm's Law, Heat, Magnetism, Light, Parallel circuit, Series circuits, Matter, Electron, Orbits, Nucleus, Atoms, Electric charge, Proton, Current, Generator, Amperes, Ammeter, Direct current, Pulsating (DC) current, Alternating Current, Voltage, Resistance, Power, Energy, Heat, Light, Electromagnetism, Induced Voltage, Meter, Voltmeters, Wattmeters, Multimeter, Voltage Drop.
The total Resistance of a Parallel circuit decreases with an increase in the number of devices operated. This is apparent since an increase in the number of paths for current results in a decrease in total resistance. Remember: The total Resistance of a parallel circuit is always smaller than the smallest resistor of that circuit. The total Resistance can be found by applying the correct voltage to the circuit and measuring the total current taken. The total Resistance is then determined by applying Ohm's Law.
Resistance of circuit = (Voltage/Current)
The total circuit resistance can be found by an application of the following formula which applies to any parallel circuit. This formula is known as the Reciprocal Formula.
Fig. 1.12
The total resistance of Circuit A can be figured by parts. The two 10 ohm loads in parallel, considered alone have a resistance of 5 ohms. Thus circuit A is equivalent to two 5 ohm resistances in-series, or a total resistance of 5 + 5 = 10 ohms.
The total resistance of Circuit B can also be figured in parts. It is two series circuits which are in parallel to each other. It is the equivalent of tm, 25 ohm resistances in parallel. Thus the total resistance is: 25 = 12.5 ohms.
The most common series parallel circuit is the control of several loads by one switch. The switch is in series with parallel loads.
[edit] ALTERNATING CURRENT PRINCIPLES
An alternating current can be generated by rotating a coil magnetic field. The voltages induced as the coil makes one revolution are shown in Fig. 1.14. The part of the graph below axis indicates voltage in the opposite direction.
Fig. 1.14
[edit] POWER FACTOR
In AC circuits, especially circuits that have large motor loads, the Apparent power is not always the same as the Effective power, as measured with a wattmeter. The effective power is often less than the Apparent power. To measure the amount that these differ we define the term power factor:
To measure the power factor of a circuit, measure the effective power with an AC wattmeter, measure the current with an AC ammeter, and measure the voltage with an AC' Voltmeter.
It is desirable to have as high a power factor as possible. A low power factor means larger conductors are needed to supply the same Power. Power factor can be corrected by installing capacitors into the system. They use no power but correct the power factor. Let the engineer in charge of the project decide when Capacitors are needed and let him decide upon the size needed. Capacitors store power. They are dangerous even when disconnected. Handle with extreme care and always with the terminals connected together.
[edit] AC MOTORS
There are many ways to build AC motors. However, they all operate on the same principle. In all AC motors an AC voltage is applied to stationary coils, which produce a varying magnetic field that changes at a speed proportional to the frequency of the current. The rotating coil rotates in an effort to line up with this changing field.
[edit] SINGLE PHASE AC
All the material about alternating current so far has been concerned with, single phase AC. The voltage reaches a maximum twice during each cycle (once in each direction). Therefore an AC motor receives two "pushes" each cycle.
[edit] THREE PHASE AC
A lawnmower engine has one cylinder. An automobile engine has six or eight. The automobile engine receives six or eight pushes per revolution compared to the single push of the lawnmower engine. It would be convenient if an electric motor could receive more pushes per revolution. This happens with three phase AC. A generator is so constructed that it generates three alternating voltages, but they reach their maximum values at different times. A three phase motor has three coils which each connect to a different "phase" of the three phase generator. Thus the motor is getting six pushes (two pushes from each phase) in the same period of time that a single phase motor gets only two pushes.
The advantage of generating three phase power is single phase power can also be obtained by connecting the circuit to a single phase, rather than all three. Also, three phase motors are more efficient, simpler, less expensive to buy and run. There are two ways to connect loads to a three phase generator. In Fig. 1.15 and Fig. 1.16 the generators are the same, the diagrams show the three coils which have voltage induced in them by a rotating electromagnet. In the diagrams the arrangement of the coils is different but only for convenience in drawing. The coils each generate 120 V. The voltages obtained with each type of connection are indicated.
Delta Connection- The delta connection of a three phase generator, which resembles the Greek letter A (Delta), is shown in Fig. 1.15.
Fig. 1.16 shows the same generator connected similar to the letter Y. This connection is sometimes referred to as a star connection.
Fig. 1.15 Fig. 1.16
[edit] TRANSFORMERS
A moving magnetic field generates an electric current in a conductor, and an alternating current flowing in a conductor produces an alternating magnetic field. These two effects can be combined in a circuit such a3 Fig. 1.17.
Fig. 1.17
One coil has a current flowing 3n it. It is an AC current that sets up an alternating magnetic field around the coil. If another coil is placed next to it, there will be an alternating current induced in it by the magnetic field. The first coil is the primary, the second coil is the secondary, and the combination is called a transformer. Most commercial transformers appear as, shown in Fig. 1.18.
Fig. 1.18
Transformers can change voltage. If there are twice as many loops in the coil of the secondary as there are loops in the primary, the voltage in the secondary will be twice the voltage of the primary. This ratio is called the turns ratio, or voltage ratio. A transformer which will change the voltage from 1,000 V. to 100 V. is called a step down transformer. A transformer that would raise the voltage would k called a step up transformer.
[edit] THE ELECTRICAL SYSTEM
An electrical system is made up of seven major parts. These are: 1. The generator plant 2. Transmission lines 3. Substations 4. Distribution lines 5. Distribution transformers 6. Secondary lines 7. The house system Each of these parts has components designed to protect or control the system. Throughout the system are switches to disconnect at of the system from the power, so that part of the system can be safely worked on. Each part of the system to protect that part from has fuses over-current. The transmission and distribution lines have lightning protectors to make lightning strikes harmless to the system.
The system is connected as follows. The generating plant is the source of power. If it must be transmitted a long-distance the voltage is stepped up at the generating plant by a transformer. This reduces the current flow through the transmission lines which decreases the voltage drop. At a substation this Voltage is reduced by another transformer and is then distributed over the distribution lines to the area where the power is to be consumed. Near the houses a distribution transformer steps the voltage down to the supplied voltage and which is supplied to the house systems.
[edit] SAFETY
Safety must be stressed at all times in all electrification work, whether or not work is being done with electrical currents present. Instructors must stress safety every time they teach a skill. They must stress safety every time they describe a procedure. Every skill and procedure has a safe way of being done and many ways that are unsafe.
This section of instruction describes how electric shock is received, why it is dangerous, and how to treat someone who has received a shock. The major protection from shock is a properly grounded system, so the theory of grounding should be taught. Exactly what to ground and how to ground it should be stressed in later sections at the time that the installation techniques are being taught.
[edit] ELECTRIC SHOCK
An electric circuit is a path through which electric current flows. When a person's body becomes part of a circuit, current will flow through his body. This current my: 1. Knock the person unconscious. 2. Give the person a bad bum. 3. Stop the person's breathing. 4. Stop the person's heart.
[edit] SAFETY PRECAUTIONS
Electricity cannot be seen, smelled, or heard, so it is impossible to tell weather a wire has one volt running through it, 1000 volts. You should treat every electric wire as if it were dangerous. Before approaching any electric wire, first study the whole electric system to see how this particular wire is connected, and if possible, measure the voltage and current in the wire with a voltmeter and an ammeter. The following DO'S and DON'TS, if carefully observed, should prevent accidents:
1. Always disconnect the electric wire from the source of current and voltage before working on it 2. Always use a test light, a voltmeter, or an ammeter to determine whether the line has a voltage In it and how much the voltage is. 3. Always wear dry gloves when approaching any electric wire. 4. Always pull the disconnected end of an electric wire well away from the source of current to create an air gap. 5. Never touch an electric wire when your feet are in water or on the ground. 6. Never let one of the three wires in a three-phase circuit touch round or one of the other wires. This sort of contact will create an electric arc and intense heat. 7. Never work on a line which has more than 250 volts running through it line-to-ground or form phase-to-phase. 8. Never replace a fuse without disconnecting all appliances and motors connected to the line. 9. Never use metal tools or wear metal jewelry (rings, I.D. bracelets.) around electric wires. Always use tools with wooden, plastic, or insulated hand grips.
[edit] RESCUE AND FIRST AID TECHNIQUES
When someone touches a "live" wire, and becomes part of an electrical circuit, the victim must first be rescued, or freed from any contact with the "live wire". He must then be promptly treated with first aid, but be very careful lest you be shocked too.
Never approach or touch the victim unless you are positive he is not in contact with the electric current. Be especially careful if he is lying in a puddle of water or on wet ground. Always pull or push the victim free of the "live wire" or wet ground with a dry, non-conductor, such as a wooden board, a rope, clothing, or lineman's rubber gloves. Never try to pull the victim free of the "live wire" or wet ground with your bare hands, a piece of metal, or anything wet or conductive. If the victim has been suffocated by gas, smokes, or fumes, move him into fresh air before beginning first aid.
[edit] FIRST AID
Once the victim is free of the "live wire", look at his eyes to see if the pupils are dilated, and check his pulse at either wrist or neck. If the pupils are dilated or enlarged and there is no heart beat, begin closed chest, heart massage immediately. Check the victim's breathing. If the breathing has stopped, start mouth-to-mouth rescue breathing at once. Do not delay to call for help, have someone else call. Do not stop!
If someone else is nearby use him. Tell him to: 1. Call a doctor. Loosen the victim's clothing. i: Cover the victim to keep him warm and comfortable. Continue rescue breathing until natural breathing starts again but stay with the victim. Breathing may stop again and rescue breathing should be started once more. Do not stop the rescue breathing if natural breathing does not begin again. Keep it up until the victim is pronounced dead by a doctor (and the American Red Cross recommends three checks for death by a doctor at lo-minute intervals) or until rigor mortis sets in. Keep the victim lying down, well-covered to keep him warm and quiet until a doctor advises that he may move, sit, or stand.
[edit] GROUNDING
Grounding means connecting a wire or piece of it to the earth. This connecting the wire, or equipment to be grounded, to a copper rod that has driven deep 20? In the earth. The earth is an adequate conductor and current will flow through it.
ELECTRICAL SYSTEMS ARE GROUNDED TO PREVENT THE DANGERS OF ELECTRICAL SHOCK AND FIRE!!!
All electrical systems should have one grounded wire. All equipment cases and covers should be grounded. All pipes, structural steel, and other conductive paths should be grounded. All of these must be connected together or grounded to the same place. When short circuits occur or when a device is connected from an energized wire to ground, the grounding wire provides a means of completing the path for the current. This completed path will allow excess current to flow which will blow one of the fuses, thus removing the current and-the danger. The grounded wire of the system must never be fused, for if this fuse should blow, the entire system would no longer be grounded, and considerable danger could be present.
Distribution systems should be grounded to a grounding electrode every 300 feet to maintain an adequate ground. generating equipment, like all other equipment, must also be grounded.
[edit] HOUSE WIRING
The learning exercises of this section and the following sections, are centered around the construction of a sample electrical system by the PCTs. The PCTs will wire two sample homes (one of mud construction) with standard techniques and techniques applicable to mud construction. These will include lighting, appliance, motor and pump installations.
This installation of a sample electrical system will be the performance test. It will also be on the job training. The emphasis should be on doing, with instruction and lecture as needed to impart information, but the instructor will primarily be advising as the PCTs install the wiring of the sample houses.
[edit] TERMINAL PERFORMANCE TESTS
1. For a given house, sketch a layout, and indicate suitable locations for switches, outlets, and service entrance components; prepare a circuit schedule, and a list of the types and sizes of service entrance components. 2. Given examples of typical locally constructed houses, select the necessary tools and materials, install the wiring and service entrance for each type of construction. 3. Given examples of wiring practices, identify and correct any unsafe practices. 4. Identify the jobs for which local workers may be used, and list the skills that must be taught for each job. 5. Install an electric water pump.
[edit] CONDUCTOR SIZES
The current that a given conductor can carry depends upon its size. The larger the diameter of a wire, the greater the current that it can carry. Wire and cable come in varying sizes I and these sizes are numbered. The higher the number, the smaller, the wire and the less current it will carry without excessive voltage drop or fire hazard. The word capacity means the maximum current a wire should carry. The following chart gives the capacities of various sized copper conductors in normal use.
For specific capacity of a wire in a specific case check manufacturer specifications. Also check the local electrical code to see if it has stricter requirements. The size of a particular wire should be marked on the cable. It can be measured with a wire gauge. A wire gauge is shown in Fig. 3.1. The widths of the openings on the rim correspond to diameters of wires whose numbers are opposite the openings.
[edit] CONDUCTOR INSULATION
All conductors used for residential wiring must be insulated. There are several types of insulation in standard use. The most common is thermoplastic insulation, which is called "Type-T". "Type-R" means a rubber or rubber compound insulation. The letters W or H following the type, indicate moisture resistant or heat resistant insulations and can be used in wet or hotter than usual locations. Thus Type-RW or type-TW can be used in wet locations; Type-THW or Type-RHW can be used in hot and wet locations; etc.
[edit] CABLES
For many purposes it is desirable to have two or more wires grouped together in the form of a cable. This is easy to install, especially when used to wire a building that was completed before the wiring is installed, for the cable lends itself well to being fished through wall spaces. All wires are marked with the size of the conductor and the type letters indicating its insulation. A cable made up of two size 14 conductors, is marked 14-2, or one with three size i2 conductors is marked 12-3, etc. The insulation type is marked on the conductor insulation and the cable type is marked on the cable sheath.
Fig. 3.2
[edit] NON-METALLIC SHEATHED CABLE
This cable consists of two or three Type-T or Type-R wires bundled together. . It costs less than other types of cable, is light in weight and very simple to install; no special tools are needed. There are two types, they are called Type-NM and Type-NMC. The first is for use in dry locations and the second is enclosed in a plastic sheath and is suitable for use in wet locations.
[edit] ARMORED CABLE
This type of cable is commonly called BX cable. It is two or three conductors of Type-T or Type-R sheathed in a spiral galvanized armor, and called Type-ACT or Type-AC respectively. The armored cable can be used in most any location that is not considered damp; there is no armored cable for use in wet locations. In such locations the use of a lead shielded cable similar to Type-NM in construction is used.
[edit] UNDERGROUND CABLE
There are two types of underground cable, Type-UF and Type-USE. These types are for underground feeders and underground service entrances. There are Type-UF cables that also meet the requirements for Type-NM. These will be marked UF-NMC. There are many other types of cable, Suited to specialty uses. These are described in the references.
[edit] COLORING OF CONDUCTORS
Conductors, separate and in cables, come in various colors, and there is a purpose for this. Only white wire may be used for the grounded neutral wire in wiring. White wire may be used when ungrounded only for feeding power to switches when cable is being used. Other wires may be any color except white or green. They occur in the following combinations: P-conductor White, Black, 3-conductor White, Black; Red 4-conductor White, Black, Red, Blue 5-conductor White, Black, Red, Blue, Yellow
[edit] WIRE HANDLING TECHNIQUES
[edit] INSULATION/STRIPPING
To connect a cable or wire in a circuit the insulation at the ends of the wire must be removed. A hacksaw is used to cut the armor on Type-AC cable. The cut is made diagonally across the sheath, cutting just one section of the spiral. The armor is then twisted off the end. To protect the conductors from the sharp edges a fiber bushing is installed between the wires and the sheathing. Type-NM cable requires a knife to remove the sheathing. A cable should have about 8 inches of sheathing removed, but care should be taken not to hurt the conductor insulation. A knife is then used to remove the insulation from the ends of the conductors, without nicking the conductor.
[edit] SPLICING
Two wires can be connected together using a splice. The most common splice is the Western Union splice shown in Fig. 3.3. It makes a good electrical contact and is strong mechanically. Fig. 3.3
A tap splice is used to connect one wire in the middle of another, as shown in Fig. 3.4.
Fig. 3.4
[edit] SOLDERING
Soldering is the bonding of two conductors together with molten solder. This makes a low resistance path for current. The steps in soldering: 1. Clean the wires to be soldered. 2. Splice the wires. 3. Clean the finished splice. 4. Heat the splice until the wires will melt the solder. 5. Apply the solder, allowing it to melt and flow through the splice. 6. rel eave the heat and allow the splice to cool. This procedure allows the solder to make a chemical bond with each of the wires. This bonding operation will be hindered if the wires or the soldering iron are not clean. Many solders contain a flux which prepares the wires for the bonding. Only the rosin flux should be used for electrical wiring, as the others tend to corrode the connection. The best solder for electrical connections if 60% tin--40% lead, rosin core solder.
Fig. 3.5
[edit] TAPING
Splices should be taped after soldering to insulate the conductor. Plastic tapes are readily available and are the best to use for this purpose. The tape should be wound around the wire diagonally and progress down the splice. This should be repeated in the other direction, and back and forth until the taped splice is the same diameter as the wire.
Fig. 3.6
[edit] SCREW TERMINALS
Most switches, and plugs have screw a screw terminal outlets, fuse terminal is shown holders, connections. in Fig. 3.7. circuit The breakers connection loop should and appliance of a wire be formed to in the wire before it is placed around the screw. When the loop is placed around the screw it should be placed so that the tightening of the screw tends to close the loop, rather than open ft.
Fig. 3.7
[edit] SOLDERLESS CONNECTORS
There are many types of connectors for joining wires that do not require soldering. These all depend upon pressure between the wires to insure a good electrical contact. It is difficult to heat the larger sizes of wire, and this nukes soldering difficult or entirely impossible. On larger sites of wire solderless connectors must be used. Fig. 3.8 and Fig. 3.9 show several types of solderless connectors. Fig. 3.9
[edit] TYPES OF SERVICE
There are several types of service that can be supplied to a consumer from the distribution or secondary lines of the system. They are: 1. 3 wire three phase (delta connection) 2. 4 wire three phase (wye connection) 3. 3 wire single phase 4. 2 wire single phase The three wire three phase service is rarely used as it provides only one voltage. The 4 wire three phase service provides three phase power at 208V. and also provides 120 V. single phase power. When three phase power is to be provided, a 4 wire service is usually the most practical. To obtain this from the three wire distribution lines, three transformers are used. The primaries of these transformers are connected in delta, and the secondaries of the transformers are connected in wye, with the neutral wire grounded. Three wire single phase service is the basic single phase service. It is obtained from the distribution lines using one transformer as illustrated in Fig. .3.10.
Fig 3.10
The 3 wire service provides two voltages. When a building requires only the lower voltage and no expansion of service is anticipated a 2 wire service can be installed using just the neutral and one of the single phase lines. In any service that uses a neutral line the neutral line must be grounded for safety.
[edit] SERVICE ENTRANCE
The term service entrance describes several pieces of equipment and their interconnection. The components of a service entrance are: 1. The service drop 2. The service insulators 3. The service head 4. The service entrance conductors 5. The meter 6. The building entrance 7. The main switch 8. The main over current protection 9. The service ground
[edit] THE SERVICE DROP
The service drop is the connection of the house system to the distribution system. This is done after the house installation is completed and tested, and is performed with the main switch open. The connection is made at the distribution system by removing the insulation on the secondary wires and making a tap splice, using solderless connectors. The service drop conductors are secured to an insulator rack on the pole, and strung to the service drop insulators and then connected to the conductors entering the service head. The service head should either be higher than the service drop, or there should be drip loops to prevent water from entering the service head.
SERVICE INSULATORS SERVICE HEAD Fig. 3.11 Fig 3.12
[edit] THE SERVICE INSULATORS
These insulators are for securing the service drop to the resistance. They should be mounted high enough on the building to allow ten feet of clearance between the service drop and the ground. They should be mounted on a secure structure of the building or on a mast or pole installed for the purpose.
[edit] THE SERVICE HEAD
This is a unit which is mounted on the top of the conduit or cable leading to the meter. Its purpose is to prevent rain from entering the conduit or cable. It should be mounted above the service insulators so that any rain will drip down the conductors and away from the service head.
[edit] THE SERVICE ENTRANCE CONDUCTORS
These include the cable from the service head, or the conductors in the conduit, to the meter and the conductors (in cable or conduit} from the meter to inside the building and to the main switch. They should be of large enough size to safely carry the current that the system will demand. Future expansions of the house loads should be considered when sizing these conductors so that the service entrance conductors will still be adequate after expansion.
[edit] THE METER
The meter should be supplied by the co-op. The meter must match the type of service being provided. If the service is just 220 V. then a meter for 220 V. should be used. If the service is for 220/440 then a 440 V. meter should be used. If the service is three phase, then a three phase meter must be provided. Most meters come with the wiring done internally and for connection all that is required is to connect the ungrounded lines in series through the connections to the meter, as in Fig. 3.13.
Fig. 3.13
[edit] THE BUILDING ENTRANCE
Whether cable or conduit is used for the service conductors they must be sealed from the weather while outside of the building and at the entrance to the building, so that no rain can enter, and possibly cause shorting of the conductors at the main switch or panel box.
[edit] MAIN SWITCH
There must be a main switch for the house system. It is necessary for disconnecting the system from the power when there is work to be done on the main fuse box or feeders of the system. This switch must be rated at the same ampacity as the service entrance conductors. If knife switches are used, they must be installed so gravity will not tend to close them.
Fig. 3.14
[edit] MAIN OVER CURRENT PROTECTION
There must be fuses or circuit conductors of the service entrance switch. Never fuse a rounded breakers in chance, after conductor, series passing if that with through fuse the un the should grounded main blow there would be no ground for the entire system and severe damage could result to the equipment of the house system. If circuit breakers are used for this function they may take the place of the main switch.
[edit] THE SERVICE GROUND
If there exists an underground water system, the installation of a system ground is easily accomplished, If there are pipes that extend underground for a distance greater than 10 feet, the system can be grounded by connecting the neutral wire at the main switch to this piping system. There should be jumpers over the pipe connections between where this connection is made and where the pipe enters the ground.
If there is no underground water system, then an electrode must be driven into the ground for the purpose. This electrode can be a piece of galvanized water pipe or preferably a copper rod, of 3/4 in. or l/2 in. diameters respectively. This rod must extend at least 8 feet into the ground.
There should be no soldered joints anywhere in the service entrance or ground, because soldering of the larger conductors is a very tricky skill. Solderless pressure connections should be used instead.
[edit] EQUIPMENT SPECIFICATION
the rating of the service entrance components must be considered before installation. Determination of the total requirements of the house is covered later in this section. This determination will indicate the maximum current that will be supplied to the system. The components of the service entrance handle all of this current and must be at least large enough to handle this maximum current. The conductors, main switch, and service ground must be able to safely handle this maximum current. The main fuses should be chosen to protect the components of the service entrance which have the smallest ratings.
[edit] SWITCH BOXES, FUSES AND CIRCUIT BREAKERS
In any installation there must be a main disconnect switch. This is necessary to allow servicing of the installation without the danger of shock. A switch box wilt allow for the disconnection of individual circuits so that they may be worked on with safety.
Fuses or circuit breakers are required on any branch circuit. They must be of a size no larger than the capacity of the conductors of that branch. They are needed primarily as fire protection in case of overload or short circuiting. They also protect the installation itself, by disconnecting the circuit before it can become so hot as to start a fire or the voltage drop become so great that equipment is damaged.
[edit] CONNECTION OF SWITCH BOXES AND FUSEBOXES
Switch boxes and fuse boxes are designed with a tommu buss for connecting all of the neutral or ground wires to. These wires must all be white. The fuse sockets, the circuit breakers, or switches must be connected in series on the "hot" lines only. NEVER fuse or switch a grounded or neutral conductor.
Fig. 3.15
[edit] ELECTRICAL SYSTEM LAYOUT
Fig. 3.15 shows an example of a house layout sketch with the layout of the electrical system indicated. You will note that the switch connection is indicated by solid or dotted lines, this denotes wiring through the walls and ceiling, or beneath the floor respectively. Other connections are not indicated shows the on the layout, but are indicated on the wiring schedule. Fig. 3.16 symbols used in house layout plans.
Fig. 3.16
[edit] LIGHTING OUTLETS
It is difficult to specify required locations for lighting outlets. There are many ways to light a room. In general, each room or area should be given a source of general lighting. This might be a ceiling fixture, several wall fixtures, or a continuous strip. In a living room or similar area the general lighting may be provided by portable units, floor and table lamps, etc., In each room, the general lighting source should be provided with control by a wall switch at the main entrances to the room. This could be done using split outlets in a living room area , where the top of each double outlet is switched and the lower has power straight from the feeders. Common sense is the best guide for the location of lighting outlets. Consider the activities that take plate in a room and decide if these require special lighting. For example, in a bedroom, light would, be needed near a mirror, preferably on both sides, in a bathroom or kitchen over the sink; or in a closet where stored material must be identified. Wall light outlets are usually located 63 inches above the floor.
[edit] LOCATION OF SPECIAL PURPOSE OUTLETS
There will be areas where there is a need for a special outlet to operate a particular appliance or machine. These should be installed at two location of the machine and meet the requirements of the machine
[edit] LOCATION OF SERVICE ENTRANCE
The ideal location for a fuse box is near the center of the house, because less wire is needed to run all the circuits. The service entrance should be located as close to this location as possible. The fuse & switch and main fuses should be just inside of the entrance of the service conductors. If the circuit fuses are located more centrally, then wire of size equal to the service conductors should be run from the main fuses to this panel box.
[edit] SAFETY
In planning the location of the various components and circuits, remember to avoid areas that would require installation in damp locations, or where the equipment or installation would be a hazard to the occupants.
[edit] INSTALLATION
[edit] JUNCTION BOXES
All outlets are installed in metal junction boxes. These have knock out slugs, which allow for entrance of the cable. All junction boxes must be securely fastened to the galls or ceilings. They are secured with wood screws to the studs or some other secure structural support. After the junction boxes are installed, the cable is run to the boxes,
[edit] SWITCH OPERATION
A switch of any type is a device for the opening or closing of a circuit. Some switches operate between several conductors, others just two. The switching of any circuit must never allow interruption of a grounded or neutral wire (white). The white or neutral wire always runs without interrupt fan by a switch, fuse or other device, up to each Point where current is to be consumed.
[edit] SINGLE POLE SWITCHES
When it is desired to control a light or group of lights, an outlet or group of outlets, from one switching point a single pole switch Is used. It is wired in series with the ungrounded (black) wire feeding the load. If there are to be several loads controlled by the one switch, the switch is in series with the parallel connected loads. (Fig. 3.17)
Fig. 3.17
Often it is desired to operate one load continuous current to an outlet further along the same circuit Fig, 3.18 illustrates such.
Fig. 3.18
[edit] THREE-WAY SWITCHES
When it is desired to operate a load (or several in parallel) from two switch locations a three-way switch is used. The wiring is illustrated in Fig. 3.19. It must be remembered that this wiring must not interrupt the grounded or neutral (white) wire, from the source. Thus the wiring involves only the "hot" wire, (black). Note that in Figs. 3.17, 3.18, and 3.19 that although a white wire is run to the switch, it is an extension of the "hot" wire (black).
Fig. 3.19
[edit] FOUR-WAY SWITCHES
Four-way switches are used with two three-way switches to control a load (or several loads in parallel) from more than two locations. A four-way switch is pictured below:
Fig. 3.20
Fig. 3.21
Note that the white or grounded wire always connects directly to the load, with one exception. The exception is using cable in switch loops where cable runs to the switches. In this case the black wire must be used between the switch and the load, the white wire between the branch feeder wire and the switch.
[edit] LOCATION OF CONVENIENCE OUTLETS
Outlets are normally located about 12" above the floor level. They should be placed near (2 or 3 feet) corners of rooms rather than in the center of the wall to lessen the chance that they will be blocked by large pieces of furniture. They also should be installed at locations where there is an expected demand.
[edit] LOCATION OF WALL SWITCHES
Wall switches should be installed about 48" above the floor level on the latch side of the doorway, within the same room as the lights it controls.
[edit] MULTIPLE SWITCH CONTROL
Any room or area with more than one entry should have multiple switch control, i.e. using 3-way and possibly 4-way switches. There should be a switch at each entrance. the fastener attached to the cable and the cable and fastener connected to the box. The cable is prepared for wiring to the outlet or switch by removing about six inches of the outer covering from the cable and removing about 3/4 in. of insulation from each conductor. Then the fastening clamp is attached at the paint where the outer cover ends. If there is a grounding wire in the cable, it should always be connected to the junction box.
[edit] OUTLETS
Lighting and appliance outlets are manufactured with a color coding There are two screw terminals for the attachment of the conductors. One screw is a whitish colored nickel, and the other is the standard brass color. The ground or neutral wire (always white) is connected to the whitish colored screw. The "hot" wire, which should usually be black, is connected to the brass screw. If there is a third, green connecting screw, this should be connected to the grounding wire of the cable, or to the junction box, which has been grounded.
[edit] SWITCHES
Switches are not cola, coded at the connecting terminals, because they are always connected in series with the "hot" lines. Therefore the terminals on a switch are brass. Switches and outlets art? connected, installed in the box, and covered with a plate that protects the consumer from contact with any of the conductors.
[edit] SPLICES
All splices made on the cables must be placed in junction boxes. This prevents the possibility of the splice being pulled apart, since the cables are securely fastened to the box. Any connections that are not made to the terminals of a switch, outlet or lamp fixture must be taped or otherwise insulated.
[edit] DROP CORDS
When wiring a drop cord ceiling outlet, an underwriters knot should be tied in the cord to prevent pulling on the connections. This knot should also be used when wiring any plug for an appliance.
Fig. 3.22
[edit] "NEW" AND "OLD" WORK
"New" work is the installation of a system in a house while under construction. "Old" work is the installation of a system in a completed house. Most of the work that will be encountered in the electrification project will be "old" work. Any concealed wiring will have to be installed in covered over areas. If allowable, surface wiring techniques will be most economical. This requires the use of Type NM or Type NMC cables, surface raceway, surface conduit, or open knob and tube work.
[edit] NM OR NMC SURFACE WIRING
With must any wood frame, or similar construction, the installation of surface NM type cable is a matter of securing the cable to the wood supports of the house. Care must be taken in running the cable, to protect it from damage, that is to keep it flush against the surface and avoid areas that will subject it to injury. This is done with straps, or staples, leaving the insulation unharmed. There should be a strap or staple every 3 feet and within 12 inches of a box.
[edit] OPEN KNOB AND TUBE WORK
Knob and tube work is very little used today. It has been almost entirely replaced by non-metallic sheathed cable. It is a wiring system using only single insulated conductors, which are run on the surface and supported by insulating knobs or cleats and when passing through holes in walls or studs, are enclosed in insulated tubes. These knobs and tubes are usually porcelain. This method is only practical when insulators and single conductors are economically available, while cable is prohibitive in price.
[edit] SURFACE RACEWAYS
Although this method is seldom seen in residences, it is a very useful method of protecting wiring done on the surface. A raceway consists of two pieces, one that Is fastened securely snaps on like a cover. The number of conductors through a raceway depends upon its size. to the wall and that may be the other one.
[edit] ARMORED CABLE (METAL CLAD CABLE)
Type-AC or Type MC cable can also be used for surface wiring, and allows for good protection of the conductors from physical damage. It is secured by staples or straps, in such a way as to avoid damage to the sheathing. It cannot be used in damp locations. The type that is usable in damp or other destructive situations, has a lead sheathing just inside the spiral armor. It is called Type ACL.
[edit] GENERAL
For all of these wiring methods, metal boxes are required for mounting the switches, outlets, lamp sockets, etc. Any splicing of wire must be done in a metal box and not in the raceways, conduits or in the open, except for knob and tube work where there must be support within 12" on both sides of the splice or tap, and the splice must be taped.
[edit] CONCEALED OLD WIRING
Old wiring that is concealed requires much extra effort in the installation. Holes must be carefully cut in the walls for the installation of the outlet boxes, and wires or cables must be fished through the spaces in the walls. Extra holes have to be drilled to allow for the cables to pass through hidden obstructions. The techniques required for concealed old work are described fn:
[edit] MOTOR SELECTION
Motors are not rated in watts as are other electrical loads, they are rated in horsepower. This is because motors consume electrical power in proportion to the amount of power they are delivering, The horsepower stamped on the nameplate of a motor is the power it will deliver continuously over long periods of time. A motor can deliver more than this for short periods but will burn out if overloaded continuously. For example, a l-horsepower motor consumes 1,000 watts while delivering the horsepower for which it was designed, in this case 1-hp.
All motors consume more power while starting than while running. Starting draws considerably more current than is drawn when running at rated horsepower. A 1-hp motor requires four times the running current for starting.
The speed of most motors is not easily adjustable. A SO-cycle motor theoretically runs at 1,500 rpm, but when delivering its rated horsepower will run closer to 1,450 rpm. A belt and pulley drive, is the most practical way to obtain the desired speed.
Motors are marked with a temperature rating. This indicates the amount the motor will heat up above the room temperature, when operating at its rated horsepower. If a motor were operating in a room with the temperature lOOoF and the motor had a rating of 40°C PF!, the motor would operate at a temperature of 172OF. Although this would seem very hot to the touch it would cause no danger for the motor.)
There are various motors for various applications. The following items should be considered in choosing a particular motor for a particular application.
1. The voltage (the higher the smaller rating of the motor and the voltages available the voltage, the less current is required and the conductors needed for service). 2. The horsepower needed for the machine being operated (if it continually requires l-hp and just for brief periods requires higher, then a 1-hp motor would be appropriate. If it would continually draw 1 l/P-hp then a larger motor [l 1/2=hp, ideally] would be needed). 3. How hard easily a starting the machine split phase a condenser being operated starts. (If it motor could be used, if it is or R-I motor may be needed). starts harder 4. The starting means smaller current required. conductors). (Less required current The most common types of single phase motors are: Split Phase Motors Capacitor Motors Repulsion-start, Induction-Run Motors (R-I motors) They are motor is listed least above in expensive order for a of price, the split-phase type given horsepower. However it of cannot start heavy loads, and it requires the largest starting current for a given horsepower. The R-I type motor can start very heavy loads and requires less starting current than any other type of single phase motor, but it is more costly.
Three phase motors cost less to purchase amp to operate than any other type. They are also much simpler in design, break down less frequently and are simpler to repair. This should be considered when deciding to supply a building, that will have motors, with single or with three phase power. Consult with the Engineer in charge of your project for advice as to which is best in a particular situation.
[edit] MOTOR INSTALLATION
There are three considerations for any motor installation. 1. There must be over current protection. 2. There must be a disconnecting switch. 3. The size of the conductors supplying the motor must be large enough to handle the starting current. Over current protection is provided by units that will shut the motor off if a high current is consumed for longer than is safe. These units are placed close to the motor and usually incorporate the start and stop controls. A separate disconnect switch must be installed to disconnect power from this equipment and the motor, so that servicing can be done without danger.
[edit] PUMP INSTALLATION
When electrical power is available pumps are conveniently operated by motors. The installation is exactly similar to the installation of a motor for other purposes. The motor may be located at a distance from the control unit. In such cases a remote control circuit may be used. It may be an automatic starting unit, which will allow for the motor operation when the water supply is low. For all these situations the basic safety procedures must still -be followed. There must be a disconnect switch that disconnects the motor and its controller from the power source. There must be over current protection for the motor. The conductors feeding the motor and control must be sized correctly depending upon the maximum current and the length of the conductors. As mentioned in the lesson on wire types, if a pump installation requires an underground run of cable Type UF or Type USE must be used.
[edit] CIRCUIT DESIGN
When designating which of the outlets in a plan should be connected to the same circuit there are several factors to consider. The main factor is the size of the loads connected to each outlet. Then consider the total load that is on a circuit. An attempt should be made to have the circuits share the total load of the house, There are other aspects to consider. Outlets in one area of the house will take less wire if they are all wired on the same circuit. The references offer many more considerations for specific situations. A large appliance may require a circuit of its own,with no other outlets on it. In a kitchen area there will be a larger demand from high wattage appliances, so a kitchen should have at least one circuit for appliances only, perhaps two. An electric range would be independently supplied. If the lighting is placed-on the same circuit there is a ready indication when a fuse does blow due to overloading.
[edit] CIRCUIT SCHEDULE
The sample of the following page is one possible circuit schedule. The important parts of any circuit schedule are: 1. Indication of what outlets are on each circuit. 2. Indication of what circuit each outlet is on. 3. Estimated load for each circuit. 4. Total load for the house.
If the system consists of two or more buildings, all powered from the same meter, there must be separate disconnect and fusing for each building, if there is more than one circuit in each building.
[edit] SAFETY CONSIDERATIONS
Safety must be considered in the design of circuits. After completing the design, check to see that no circuit draws more current than the wire size can carry. Make sure that the fuse for each circuit is no larger in size than the rating of the circuit's wires. Check the specification of each outlet, switch, and other components to see that they are not too large or too small.
[edit] TOTAL LOAD REQUIREMENTS
The total load requirements of a house or compound system must be determined before installation. The service entrance must be sized depending on the total load requirements. The total load of the house or compound can be divided into four areas: Lighting, Small Appliances, Heavy Appliances, Motors.
[edit] LIGHTING
To determine the total lighting requirement, a formula can be used. Allow 3 watts for, each square foot of floor area, using the outside dimensions of the house. Thus a two story house which measures
25 x.30 x 2 stories x 3 watts/sq. ft. = 4,500 watts.
[edit] SMALL APPLIANCES
A small appliance is defined to be any appliance that does not have a circuit for it alone. Standard practice allows 3,000 watts for the total to be used by small appliances.
[edit] HEAVY APPLIANCES
This term includes any permanently installed equipment, water heater, dryer, farm equipment, heating, etc. The heavy appliances load is determined by adding the individual loads of each appliance.
[edit] MOTORS
For the purpose of determining the total load requirements for the motors in a home or compound, the following table should be used. This chart is designed only for determining approximate total load requirements, these figures allow for adequate service entrance ampacity. Motors run using less wattage, these figures allow for starting and overload.
[edit] NAMEPLATE INFORMATION
All electrical devices have a nameplate. On lamps and some other devices the nameplate is printed directly on the device. Most other devices have a small metal plate mounted on ft. Examples of nameplates are shown In Fig. 3.23.
Fig. 3.23
The translation of the motor nameplate data above is as follows: A l/2-hp motor to operate from a 115-volt 60-cycle AC single phase source, the full load current is 7.5 amp and the full-load speed is 1,725 rpm. The model number is lE166A and the frame number is 562. It is a utility motor type and is rated for continuous operation with a normal temperature rise of 50°C above room temperature. The service factor (SF) is the multiplier, indicating the amount of overload permitted for the motor (1.0 x l/2 hp = l/2 hp, no overload permitted).
[edit] CONSUMER EDUCATION
When the project is near completion the consumers must be taught the use of electrical power. They must be educated about the nature of electricity, and the safety precautions that they must follow in their use of electricity.
When electrical power was first introduced in many parts of rural USA there were many reactions. Some people didn't know that there were switches that could turn their lights on and off. Some thought if a lamp was missing from a socket, electricity must be running out all over themselves and the floor. A simple lesson in electricity explaining what a complete circuit is, and that a break in the circuit causes no flow, but no waste would be helpful. It must be explained how to change fuses , why they blow and how to correct the situation before they are replaced. The safety that fuses provide, and the severe danger of pennies in fuse sockets must be stressed. If the co-op supplies the fuses free, their use would be encouraged rather than their disuse.
[edit] POWER DISTRIBUTION SYSTEM
As in the previous section the emphasis of this section is doing. The PCTs will be digging pole holes, erecting the poles, and stringing the lines for the sample distribution system. They will also install needed equipment such as transformers, fuses, and lightning arresters.
In an effort to reduce the length of the training period it is recommended that the PCTs actually dig only one or two of the necessary holes for the poles and anchors. It is recommended that a professional crew be hired to dig the remaining holes with a truck mounted power auger. This operation would be observed by tie trainees and discussion of the methods used by the professional crew encouraged. The remainder of the installation should be handled by the PCTs.
The design of the distribution system should be the responsibility of the engineer in charge of the project. This section considers briefly the design of the system, in order to give the PCTs needed background knowledge.
[edit] MAP MAKING
The following describes the construction table. Such maps are valuable for village route of distribution lines, of serviceable layout plans, maps using and planning a plane the following tools and materials are needed: Plane table, Paper, Pencil, Ruler, Pins, Tape measure, Spirit level.
Lay out a one hundred foot interval on level ground, an uphill, and a downhill slope. If only a foot ruler is available, this may be used to mark out three or four feet on a stick, and this stick in turn used to measure the 100 feet. Being careful to work normally, the map maker then determines the number of paces over the 100 foot interval for each slope. By division, it is then possible to find a number of feet in an average pace or uphill, level, and downhill slopes.
The next step is to decide on a scale for the map. This is determined by judging the longest distance to be mapped and the size of the map desired, It should be noted that the map does not have to be made on a single sheet of paper but can be splice< together when completed. As an example, if one wanted a map 2 l/2 feet long to portray an area whose major distance is l/2 mile, 2640 feet, then a scale of 100 feet to the inch would be convenient.
Paper should be placed on the plane table and the plane table oriented on or near some principal feature of the map, that is, a path, road, creek, street, etc. A pin should then be placed vertically in the spot on the finished map where this location is desired. The plane table should be made level -by use of a spirit level, if available. The table should be rotated to a proper orientation, that is, so that the direction will appear on the finished map in the desired way. Now sight along the first pin to another principal feature which is visible from the table location (a bend in the road, a hill or any feature that will tie the map together), moving the second pin into the line of sight. A ruler may be used for this purpose if it has a sighting edge or even a couple of pins stuck into it. How draw a line in tile direction defined by the two pins. Measure the distance to the feature observed either by pacing or with a tape. Scale this distance along the line drawn, starting at the initial pin. Repeat this process for other principal features which may be seen from this location. When this has been done move the table to one of the points just plotted, selecting one which will enable you to move over the territory in a convenient fashion. For example, follow a lane or creek or some feature which ties things together. Set up the plane table over this point and reorient the table. Do this by putting pins into the map at the present and previous locations. Next rotate the table so that the pins line up with the previous location. This procedure in fact locates the line joining the two locations on the map in the same direction as the line exists in nature. Again from this new location map in the desired features which can be conveniently sighted.
In this way the entire region to be mapped may be covered in a systematic way. If gaps appear or if more detail is needed, you may go back and set up over some mapped feature , reorient the map by sighting on a second feature, and proceed to map in the detail.
Fig. 4.1
An alternate procedure may be used in mapping features which are not going to be used as plane table locations in the mapping process. This involves drawing a line in the direction of each feature from two plane table locations. The intersection of these two lines corresponding to a single feature locates the feature on the map. As a result this avoids the necessity for measuring distances. Note, however, that it is impossible to avoid measuring the distances between plane table locations. If a spirit level is available, it is possible to level the plane table accurately, and using a ruler or other sighting device, relative elevation may be plotted on the map. A stick about six or eight feet long should be marked off in inches, and the person holding the stick vertically can, by moving his finger, identify to the person sighting, the distance up from the ground through which the line of sight passes.
A topographic map is a means of illustrating, through the use of contour lines, the shape of the ground surface. Many other kinds of numerical geophysical and geological data also lend themselves to the contouring method of expression. This exercise involves the determination of ground relief (topography) from points whose elevations above sea level are known. (You will need to know the basics of reading a topographic map.)
Fig. 4.2
The method is called "contouring from spot elevations'. The might have been obtained by surveying with a plane table, although w3ern topographic maps are made much more easily and accurately by the stereoscopic plotting of air photo information.
A set of rules and hints in topographic contouring are: 1. All points lying on a contour are of the same elevation above (or below) mean sea level which is taken as the reference horizon. However, one contour need not satisfy all the points of equal elevation; e.g. adjacent hilltops of similar height might require separate, closed contours each showing comparable levels. Some contours may be cut by the edges of the map and appear, to be discontinuous but if the map be mad large enough every contour eventually closes on itself, becoming continuous. 2. With rare exceptions, the contour interval is constant for the map area and is defined as the vertical distance between successive contours. The contour interval is stated as part of the scale of the map so that the vertical dimension of the contoured surface has identical l0 foot, 20-foot, 50-foot and l00-foot intervals are common. The interval is selected to best show the shape of the surface at the desired horizontal scale without requiring an unnecessary, unreadable number of lines. The relief of the area to be mapped also influences the choice of the contour interval. 3. Contours do not cross. Such a situation would illustrate an impossible ground surface shape. Contours are closely spaced on steep slopes, and distantly spaced on gentle slopes. 4. Closed depression contours are hachured (See Fig. 4.2) on the lower side. They are used when all points within-the line are below the level of the line. Obviously they are only required to show depressions which are completely surrounded by high ground. Gullies and river valleys are not illustrated by depression contours. A depression contour takes its value from that of the lowest, topographically adjacent regular contour. 5. In contouring gullies and valleys, the contours vees in the upstream direction. Be careful to confine the stream to the lowest part of its valley by passing the stream through the notch of the vees. Fig. 4.3 Contours are broken where numbering is necessary, to improve readability. 6. The use of some degree of "artistic license" is recommended in contouring. Do not attempt to just satisfy the point data. Try to make the trend of a contour reflect the trend of its neighboring contours.
[edit] SELECTING THE ROUTE
The first step to be taken in the design or construction of any electric power line is to survey and map the country over which the line is to pass. With the map completed, the following principles should be used as guides in selecting the exact route: 1. Select the Shortest Route Practicable. The shortest line naturally is the cheapest, other things being equal. 2. Parallel Highways as Much as Possible. This makes the line readily accessible both for construction and for inspection and maintenance. 3. Follow Property Lines. This causes less damage to farmers' property and crops and often prevents legal squabbles. 4. Route in Direction of Possible Future Loads. If there is possibility of adding future loads. The route selected should be as close as-possible to the locations which will require electricity in the future. 5. Avoid Crossing Hills, Ridges, Swamps, and Bottom Lands. Lightning and storms are likely to hit lines on bills and ridges. Floods may affect lines in swamps and bottom lands.
[edit] CLEARING THE ROUTE OF THE LINE
Practically all lines will cross through some brush or timberlands. A line built in such terrain must have its route cleared before construction can be started. In clearing the route, all stumps should be cut low. All logs and brush should be cleared away for ten feet on either side of the pole line to make room for assembling and erecting poles and stringing wires. All dead limbs and branches near this cleared pole line should be cut down because a high wind may blow them into the line. Brush killing sprays may be sprayed on the base of shrubs and small trees to a height of 12 to 15 inches above ground.
[edit] LOCATING POLE POSITIONS
In locating poles, the following general principles should be kept in mind: 1. Select high places (avoid lowlands, swamps, etc.) 2. Keep "spans" uniform in length. ("Spans" are the distances between poles . This prevents the weight of the wire on one side from pulling the pole over). 3. Locate to give horizontal grade. (See Figure 4.4) Locate the poles on knolls or high places* so that shorter poles can be used to maintain the proper ground clearance at the middle of the span, (The ground clearance should be at least 18 ft. at middle of span). Avoid ravines and low places where the footing is bad.
In rolling country, the location should take into account the grading of the line. A well-graded line does not have any abrupt change, either up or down. The permissible difference in level between adjacent line poles is usually limited to 5 or 10 ft. This eliminates the necessity of using guys to counteract the strain of the different levels of line conductors. A difference of 5 ft. is allowed on spans of 150 ft., and 10 ft. on spans of 250 to 300 ft.
Fig. 4.4
Special attention should be given to the location of poles where the ground washes badly. Poles should not be placed along the edges of cuts or embankments or along the banks of creeks or streams. When it becomes necessary to set poles on the edge of a cut, the pole should be set deep enough to protect the line in case the bank washes or crumbles away. After the exact pole positions have been fixed, drive a stake to indicate the center of the pole.
[edit] CHOOSING THE POLE
A pole or line support is simply a device to keep electric lines off the ground. Overhead electric lines are desirable for a number of reasons. It is safer to keep electric lines out of the hands of untrained people and roads and houses can be built beneath them. Any type of structure that keeps electric wire above ground is better than running the wire directly on the ground. The following list gives line support materials from the most desirable to the least desirable: 1. A 20 ft. standard wood pole (treated with wood Preservative). 2. A 20 ft. length of 4' x 4" lumber. 3. The corner of a building -wire mounted 12 ft. above ground, 4. A metal pole properly grounded (steel, aluminum, etc.). 5. A living tree.
Tree limbs falling into overhead wires cause the majority of low voltage power interruptions. For this reason do not use trees as line supports. If living trees must be used, trim the tree extensively almost to the point of stripping the tree to the trunk. Do not use a dead tree because it is very likely to be weak and rotten.
[edit] POLE HAULING
Poles can be hauled in several ways. They can be supported several feet below the mid point by a trailer, then towed behind a truck or jeep by securing the top of the pole to the vehicle. For shorter hauls a "timber hitch" (Fig. 4.5) can be tied around the butt of the pole and tie the rope to the yoke of an ox team, or a jeep.
Fig. 4.5
[edit] POLE PREPARATION
The typical electric pole consists of high voltage wire supported on cross arms and low voltage wire mounted on racks of insulators below the cross arms. (Fig. 4.6)
Fig. 4.6
[edit] TRIMMING
Trimming is required if the pole is in an unprepared state. Trimming is the stripping off of all the bark and knots.
[edit] ROOFING
Roofing is the cutting of an angle on the top of the pole so that water, or perhaps snow or ice, will not collect on the top, thus preventing decay. In Fig. 4.7 there are several examples of roofs. Roofing is unnecessary if the entire pole is treated with wood preservative such as creosote.
Fig. 4.7
[edit] GAINING
Gaining is the notching of a pole so that a crossarm or other piece of hardware will mount flush against the pole.
[edit] PRESERVATIVE
A pole will last much longer if it is treated with a preservative. This will protect it from rot, and termites. The section of the pole that will be under ground level must be painted with a wood preservative. Ideally the whole pole should be so painted. Before a pole is erected as much preparation as possible should be done. The work is much easier to do on the ground with firm footing than it is in the air, after the pole has been erected. The preparations should include: trimming, roofing, gaining, boring of all needed holes for bolts, painting with preservative mounting all close fitting equipment, i.e. insulator racks, guy wire bolts, etc.
[edit] DIGGING THE POLE HOLE
The diameter of the hole is determined by the size of the large end of the pole. The hole should be large enough to allow plenty of space on each side of the butt of the pole for tamping the soil back into the hole. This requires at least 3 in. all around the butt. The diameter of the hole should be fairly uniform from top to bottom, How deep the hole should be is determined by the length of the pole and by the holding power of the soil or earth. The recommended depths of setting in soil and rock are given in Table 4.1 for various pole lengths from 20 to 50 ft.
Table 4.1
[edit] RAISING THE POLE (Pike Method)
The piking method is the oldest method of raising poles. It gets its name from the so-called "pike pole" used by the men raising the line pole. A pike pole is a long pole with a steel spike on the end of the pole. A "jenny"', a sort of heavy shaft with a IJ on the top end, is also used to support the pole.
Fig. 4.8
A "piking" crew always has one man at the butt of the pole and one man at the "jenny" --a "jennyman." The number of "pikers" depends upon the length and the weight of the line pole to be raised. Table 4.2 gives recommended crew sizes.
Table 4.2
The first step in raising a pole using the piking method is to lay the butt end of the pole over the hole against a bump board or bar which rests on the bottom of the hole and extends over the top, as shown in Fig. 4.9. The board or bar protects the walls of the hole and prevents them from being caved in by the butt of the pole as the pole is raised.
Fig. 4.9 In the pole tree second support limb with step the pole a fork pole in is raised support, or the small by jenny, end hand and is The main placed on the initially a heavy duty of the man at the butt is to keep the pole from rolling. This is done by means of a cant-hook--See Figure 4.10.
Fig. 4.10
In the third step the men stand side by side on either side of the top end of the pole. They then lift the top end of the pole as high as they can while the jennyman slides the jenny toward the butt. The jennyman supports the pole between lifts. In this manner they move along the pole until the pole is high enough to require the use of pikes.
The fourth step is to punch the pikes into the pole and prepare to raise the pole. As the pole is raised, the man carries the jenny forward always ready to support the pole if need be. The raising continues until "high pike" is called by one of the men. This means that the top of the pole is so high that he can no longer push it with his pike pole. The jennyman then sets the jenny to support the pole and while the other pike men hold it steady, first the man nearest the butt releases his pike and steps forward for a fresh lift closer to the butt. The other pike men follow in order and when all are ready they lift once again. The pole is raised in this manner until it drops into the hole.
Fig. 4.11
[edit] POLE SETTING
When setting the pole after it has slid into the hole there are several things to keep in mind. First the pole should be faced. This is turning the pole with the cant hook, until the gains or the insulator racks are lined up facing the direction of the lines that will pass through them, The pole should then be straightened, or plumbed. This is to adjust the pole with the pikes until it is in a vertical position. This is done by the piking crew with a "foreman" standing away and giving directions. Once the pole is plumb the butts of the pikes should be jammed into the ground so that they support the pole without assistance.
Then the pole is ready to have the hole filled. In some soils there will be a need for cribbing as in Fig. 4.12. It cannot be stressed too much that the fill shoveled back in the hole must be well tamped, This is pounding down of the fill with rods until it is very hard packed. There should not be any soil left over if enough tamping is done.
Fig. 4.12
Many utility accidents and fatalities are caused by linemen falling from line poles. With this as a preface, we can now discuss the proper way to climb a line pole. Climbing a line pole is extremely dangerous and the use of a ladder is much more desirable for the novice electric lineman. The ladder should be so placed that the distance from the base of the pole to the bottom of the ladder is 1/3 the distance from the base of the pole to the top of the ladder. (See Fig. 4.13). Before working on the pole from the top of the ladder, the ladder should be tied securely to the pole.
Fig. 4.13
Teaching the techniques of climbing poles with a pair of "climbers" is beyond the scope of this manual. (instructor's Note: If these techniques are deemed necessary to the PCVs training, local utility personnel should be contacted and brought in to teach these techniques.)
[edit] GUYING THE POLE
Guys should be used whenever there is stress on a pole that tends to pull it out of line. Dead ends or corners should be guyed as to pull the pole over. Guys should also the weight of be used at the road lines or railroad tend crossing. "Crossarms" may need guying if there is an unbalanced pull on them. Examples of these are shown in Figs. 4.14.-4.19
Fig. 4.14
Guy wire installed on a distribution line to counterbalance the pull of the "dead-ended" distribution wires. (Side view).
Fig. 4.15
Wire guy installed on a terminal or end pole. (Top view).
Fig. 4.16 Guy installed at angle in line.
Fig. 43 Guying a corner pole
Fig. 4.m installed on crossarm.
Guying to strengthen pole line installed on steep grade. There are four steps in the installation of a guy: 1. Digging in the anchor 2. Inserting the insulators 3. Fastening the guy to the pole 4. Tightening the guy and fastening to the anchor
[edit] DIGGING IN THE ANCHOR
There are several types of anchors, some are illustrated in Fig. 4.20. Additional sections of pipe might be necessary to reach a depth giving the required holding power.
Fig. 4.20
The most economical anchor when labor is inexpensive is the log type anchor. It is also the most effective anchor. Its installation will be described here. The installation of the others is explained in Kurtt's Handbook. A trench is dug a minimum of 4 feet deep. After having a hole bored in the log to pass the anchor rod through, the log is laid in the trench. The anchor rod is driven through the ground at the proper angle, and is secured through the log with a washer and nut. The trench is then filled and well tamped.
[edit] INSERTING THE INSULATORS
Insulators must be installed in a guy whenever there is the possibility of live wires falling and coming in contact with a guy. The insulator should be placed to insulate that portion of the guy from ground. The two sections of guy are looped through the separate parts of the insulator and the ends clamped to the guys.
[edit] FASTENING THE GUY TO THE POLE
The easiest method is to bore a hole for a bolt in the pole at the point the guy is to be attached. Loop the guy wire through the eye of an eye bolt and clamp the end to the guy. Then install this eye bolt through the pole. There are other pieces of hardware available for fastening a guy to a pole.
[edit] TIGHTENING THE GUY AND FASTENING TO THE ANCHOR
A wire grip is used with a block and tackle to pull the guy taut. The guy is tightened until the pole is pulled over slightly toward the WY* Then when the line conductors are strung later the pole will stand erect under the combined strain of the guy and the line. Once taut, the guy is looped through the anchor rod and clamped.
Fig. 4.21
[edit] JOINING LINE CONDUCTORS
Line joints can be divided in three classes:
1) Splices. 2) Sleeve joints. 3) Compression joints.
Small-sized copper wires can be spliced, but the larger sizes of copper wire are usually joined by means of splicing sleeves or compression joints.
[edit] MAKING A SPLICE JOINT
In the case of covered wires, the two ends of the wires to be spliced should be scraped perfectly clean and free from insulation. The &res should be cleaned until they are