ELECTRICAL INSTALLATIONS Grp 1: aadhar, aum, kushik, gauri, insha, janhvi, sania (sem : IV) WIRING SYSTEMS Submitted by: sania(19/AR/16) What is Electrical wiring system ? ● ● ● Electrical wiring is generally refers to insulated conductor used to carry current and associated device. Domestic electrical appliances like lights, fans, washing machines, water pump, etc are connected to the supply through insulated wires which are controlled by switches. This wiring diagram gives the connections of different appliances to the supply within a house or building. TYPES OF WIRING ● ● ● ● ● Cleat wiring Wood casing wiring CTS wiring or TRS wiring or Batten wiring Conduit wiring Metal sheathed wiring or lead sheathed wiring CLEAT WIRING WOODEN CASING WIRING CTS wiring or TRS wiring CONDUIT WIRING METAL SHEATHED WIRING OR LEAD SHEATHED WIRING OPEN WIRING CONCEALED WIRING CIRCUITS ADHAR TYAGI(19/AR/01) CIRCUITS A closed circuit is a complete electric circuit that allows electrons to flow along an uninterrupted path. Electrons will only flow if the circuit is complete with no gaps SIMPLE CIRCUIT Here is a simple electric circuit. It has a cell, a lamp and a switch. To make the circuit, these components are connected together with metal connecting wires. cell lamp switch wires TYPES OF CIRCUIT Devices within a circuit can be connected in one of two ways: ● Series ● Parallel Series circuit Devices form a single pathway for electrons to flow Parallel circuit Devices form branches, each of which is a separate path for the flow of electrons Wiring diagram A wiring diagram is a simple visual representation of the physical connections and physical layout of an electrical system or circuit. It shows how the electrical wires are interconnected and can also show where fixtures and components may be connected to the system. Wiring diagram representation Load capacity The term "electrical load capacity" refers to the total amount of power provided by the main source of electricity for use by your home's branch circuits and the lights, outlets, and appliances connected to them. Load calculation Calculating how much power your home needs is a matter of calculating the amperage load of all the various appliances and fixtures, then building in a margin of safety. Generally, it's recommended that the load never exceeds 80 percent of the electrical service's capacity. To use the math, you need to understand the relationship between watts, volts, and amps. These three common electrical terms have a mathematical relationship that can be expressed in a couple of different ways: ● Volts x Amps = Watts ● Amps = Watts/ volts These formulas can be used to calculate the capacity and loads of individual circuits, as well as for the entire electrical service. For example, a 20-amp, 120-volt branch circuit has a total capacity of 2,400 watts (20 amps x 120 volts). Wiring material & Lighting accessory : Wire & Cable, materials ,types, main switch Submitted by: Kushik Mishra (19/AR/08) Types of wire used in wiring Vulcanized Rubber wire A Vulcanised Rubber wire mainly consists of a tinned conductor having rubber coating.Tinning of conductor prevents the sticking of rubber to the conductor.Thickness of rubber mainly depends on the operating voltage to which wire is designed.A cotton bradding is done over the rubber insulations to protect the conductor against the moisture. Finally the wire is finished with wax for cleanliness. Weather proof wire •It made waterproof by drooping it into waterproof compound •It is useful for service connection Lead covered wire •No effect of moisture on it •It used where there is moisture presence. Mineral insulated copper covered •Less effect of temperature. •Copper sheath is provided. •It is used in mines, factory, refinery, furnace, boiler, rolling,mill etc. •Coating of magnesium oxide is provided. Poly Vinyl Chloride wire •Dielectric strength is more •Mechanical strength is more •Life is long •Protect against flame •Protect against oil, alkali •PVC wire is widely used Lighting Accessory INCANDESCENT LIGHT FLUORESCENT LIGHT LED DISCHARGE LIGHT PENDANT LIGHTS ISLAND POOL TABLE LIGHTS HALOGENS CHANDELIERS CEILING MEDALLIONS SCONES FLUSH MOUNT LIGHTS SEMI FLUSH MOUNT LIGHTS TRACK LIGHTING MAIN SWITCH MAIN SWITCH : This switch is used to switch “ON or OFF” the main supply . These switches are used to control the whole supply for a house , office and machine . In single phase circuit I.C.D.P main switches are used, whereas in three phase circuits I.C.T.P. main switches are used to control the supply. Design consideration of electric installation Protection against overload,short circuit and earth fault By Gauri Patra, 19/AR/004 Types of loads ● Domestic Purpose The electricity for domestic purpose is consumed in various types of loads such as: (1)Single phase 5 A domestic Lighting load: -For lighting Filament lamps , fluorescent tubes , fans. (2)Single phase 15 A power domestic load: -In case of air conditioning , electric water heating , refrigeration. (3)Commercial load: (i)Shops (ii)Offices (iii)Schools (iv)Colleges (4)Street light load : This is under Gram-Panchayat ;Municipality or corporation . A separate line is provided for this purpose and is charged in a different type of tariff. (5)Agricultural load :This is generally 3 phase 440 volts ,pumping motor load (6)Rice mills /Sawmills : For this a 3 phase 440 volt 3-phase service line is separately provided. (7)Industrial load: (a)For small scale industries / workshops (b)For medium scale industries (c)Large scale industries Electric supply system ● ● ● ● 250 V or less : LV 251 V to 650 V : MV 651 V to 33 kV : HV Above 33 kV : EHV DISTRIBUTION SYSTEM ● ● ● Single phase ac supply using a 2 – wire system; Three phase ac supply using 3 – wire system; Supply of Three phase and neutral using a 4 wire system. DC SUPPLY ● ● A two wire system at 220 V A three wire system with 440V between the two outer conductors and 220V between the outer conductors and the centre wire. Supply voltage ● ● Single phase : 240 V, 50 Hz, 2 wire Three phase : 415V , 50Hz, 4 wire Consumers with load requirement more than 250 kVA are provided with supply at high voltage with a substation installed in the consumer's premises where voltage is stepped down to 415/240 V ● ● In India and many European countries the frequency of the supply is 50 Hz In USA 60 Hz VOLTAGE TOLERANCES ● ● ● Current carried by the electrical power distribution network varies at different times of the day. It leads to varying voltage drops in the supply cables. Under IE Rules voltage fluctuations may not vary by more than 5 % above or below the declared nominal voltage , frequency 1% from 50 Hz Conductors and cables ● ● ● ● All conductor must me surrounded by insulators In overhead the air act as insulation. Insulation requirement at supports through which lines are suspended from the ground The conductor with insulation- A Cable Mostly used insulation in cables are – Paper (earliest material, works as good insulator as long as it is kept dry) - Rubber ( from 1910 to 1950) - Plastics ( most common PVC) For cables for withstanding high temperatures we use silicon- rubbers STRANDED CONDUCTORS ● ● Stranded conductor consist of no of Cu or Al wires place together like a rope. Stranding is employed to make the cable flexible Stranded conductor is expressed as 3/.029, 7/.026 etc first no.represent no.of strands and second no gives the diameter of each strand in inch or mm. Parts of a conductor Rating of cables ● ● ● Cables are always assigned a rating. For rubber and plastic insulated cables rating is based on the temperature which the insulation can withstand. When several plastic insulated cables run together in the same duct or conduit, rating may be reduced since each will tend to heat each other . CRITERIA FOR SELECTING CABLE ● ● It should be able to carry maximum expected current without the insulation getting damaged. Voltage drop inside the cable should be permissible. VOLTAGE DROP ● ● Depends on current , cross sectional area of the cable, and its length. Voltage drop between supply point in any building and any outlet should not be more than 2.5% of the nominal voltage. PROTECTION OF ELECTRIC INSTALLATIONS AGAINST OVERLOAD, SHORT CIRCUIT AND EARTH FAULT Basic considerations ● ● ● There should be ready means of isolation of a circuit in the event of any accident or for the purpose of servicing. This is provided by means of switches. Conductors used should have adequate size. ie. Cross sectional area so that the current they will carry will produce minimum heat and voltage drop. Protection should be provided against excess current and electric shock. Excess Currents ● ● ● ● ● Rated current for a wire is that value of current which does not cause the temperature of the wire to reach a value which would damage the insulation. Any value of current which causes the insulation to be damaged is called excess current or overload current. The wire size selected according to a certain expected load. If the load exceeds this value, system will draw the excess current. Value of current depends on the extend of overload Causes of overloads and short circuits Causes of overloads ● ● ● ● ● By switching on heating or light loads of higher power rating. By switching on a large no of heating or lights than what the wiring designed for. Mechanical overloading of motors. Mechanical faults in the motor. Due to large friction at bearings & Jamming of rotor. Short circuits ● ● When two phase wires or phase wire to neutral wire make direct contact. Fuses are used to prevent damage, fire. Earth fault ● ● When the phase wire makes contact with earth or any conducting material which is earthed, a short circuit exist between the wire and earth called earth fault Fuses are used to interrupt large current caused by earth fault. Fuses and circuit breakers ● ● ● ● ● When the excess current is very high the operating time is very short. When the excess current is small the operating time is longer When short circuit occurs the resulting current will be extremely high and its flow should be arrested in shortest possible time When extra load is switched on which may draw say 25% higher than the rated current. This current will not cause any immediate damage, the protective device should act after a time lag. Topic 7 - Method Of Earthing, Fuse, Types Of Fuse, Guidance For Installation Of Light And Fitting By Janhvi Singh (19/AR/06) EARTHING Earthing or grounding is the process of transferring the immediate discharge of electricity directly to the earth plate, by means of low resistance electrical cables or wires. The electrical earthing is done by connecting the non-current carrying part of the equipment or neutral of supply system to the ground. The earthing is essential because of the following reasons:•The earthing protects the personnel from the shortcircuit current. •The earthing provides the easiest path to the flow of shortcircuit current even after the failure of the insulation. •The earthing protects the apparatus and personnel from the high voltage surges and lightning discharge. METHODS OF EARTHING 1) PLATE EARTHING In plate earthing system, a plate made up of either copper with dimensions 60cm x 60cm x 3.18mm (i.e. 2ft x 2ft x 1/8 in) or galvanized iron (GI) of dimensions 60cm x 60cm x 6.35 mm (2ft x 2ft x ¼ in) is buried vertical in the earth (earth pit) which should not be less than 3m (10ft) from the ground level. For proper earthing system, follow the above mentioned steps in the (Earth Plate introduction) to maintain the moisture condition around the earth electrode or earth plate. 2) PIPE EARTHING A galvanized steel and a perforated pipe of approved length and diameter is placed vertically in a wet soil in this kind of system of earthing. It is the most common system of earthing. The size of pipe to use depends on the magnitude of current and the type of soil. The dimension of the pipe is usually 40mm (1.5in) in diameter and 2.75m (9ft) in length for ordinary soil or greater for dry and rocky soil. The moisture of the soil will determine the length of the pipe to be buried but usually it should be 4.75m (15.5ft). 3) ROD EARTHING it is the same method as pipe earthing. A copper rod of 12.5mm (1/2 inch) diameter or 16mm (0.6in) diameter of galvanized steel or hollow section 25mm (1inch) of GI pipe of length above 2.5m (8.2 ft) are buried upright in the earth manually or with the help of a pneumatic hammer. The length of embedded electrodes in the soil reduces earth resistance to a desired value. 4) EARTHING THROUGH THE WATERMAN In this method of earthing, the waterman (Galvanized GI) pipes are used for earthing purpose. Make sure to check the resistance of GI pipes and use earthing clamps to minimize the resistance for proper earthing connection. If stranded conductor is used as earth wire, then clean the end of the strands of the wire and make sure it is in the straight and parallel position which is possible then to connect tightly to the waterman pipe. 5) STRIP OR WIRE EARTHING: In this method of earthing, strip electrodes of cross-section not less than 25mm x 1.6mm (1in x 0.06in) is buried in a horizontal trenches of a minimum depth of 0.5m. If copper with a cross-section of 25mm x 4mm (1in x 0.15in) is used and a dimension of 3.0mm2 if it’s a galvanized iron or steel. If at all round conductors are used, their cross-section area should not be too small, say less than 6.0mm2 if it’s a galvanized iron or steel. The length of the conductor buried in the ground would give a sufficient earth resistance and this length should not be less than 15m. FUSE In electronics and electrical engineering, a fuse is an electrical safety device that operates to provide overcurrent protection of an electrical circuit. Its essential component is a metal wire or strip that melts when too much current flows through it, thereby stopping or interrupting the current. It is a sacrificial device; once a fuse has operated it is an open circuit, and must be replaced or rewired, depending on its type. Working Principle: Melting Of Internal Conductor Due To Heat Generated By Excessive Current Flow. TYPES OF FUSE The fuses are mainly classified into two types, depends on the input supply voltages they are the AC fuses and the DC fuses. DC Fuse The DC fuse opens or breaks the circuit when the excessive current flow through it. The only difficulty with the DC fuse is that the arc produced by the direct current is very difficult to extinct because there are no zero current flows in the circuit. For reducing the DC fuse arcing the electrodes are placed more distance apart due to which the size of the fuse increases as compared to AC fuse. AC Fuses The AC fuses are categorised into two types they are the low voltage fuses and the high voltage fuses. The frequency of the AC fuses changes it amplitude from 0º to 60º in very one second. Thus, the arc extinction in the AC circuit can be done easily as compared to the DC circuit. The low voltage fuses can be further divided into four classes shown below in the image Semi-enclosed or rewirable type and totally enclosed, or cartridge type switches are the most commonly used switches. 1) Rewirable Fuses This type of circuit is mostly used in the small current circuit or for domestic wiring. The fuse case and the fuse carrier are the two main parts of the rewirable fuse. The base of the fuse is made up of porcelain, and it holds the wires which may be made up of lead, tinned copper, aluminium or alloy of tin-lead. The fuse carrier can be easily inserted or taken out in the base without opening the main switch. 2) Totally Enclosed or Cartridge Type Fuses The fuse element is totally enclosed in an enclosed container, and it has metal contacts on both sides. These fuses are further classified as D-type cartridge fuses and the Link type cartridge fuses. 2.1) D-Type Cartridge Fuses The main parts of the D-type fuse are the base, adapter ring, cartridge and a fuse cap. The cartridge is kept in the fuse cap, and the fuse cap is fixed to the fuse base. The cartridge tip touches the conductor when it is completely screwed to the base and thus completes the circuit through the fuse links. 2.2) Link Type Cartridge or High Rupturing Capacity In such type of fuses, the fuse element carries the fault current for a long duration. If the fault is not clear, then the fuse element will melt and open the circuit. The major advantage of HRC fuse is that it clears the low as well as a high fault current. HRC fuse has the high-speed operation and also does not require maintenance. But the fuse element of the HRC fuses needs to be replaced after each operation, and it also produced the heat during the faults which will affect the operations of the nearby switches. The enclosure of the HRC fuse is filled with powdered pure quartz, which acts as an arc extinction medium. The silver and copper wire is used for making the fuse wire. The fuse wire has two or more sections which are joint by using tin-joint. The tin-joint reduces the temperature under overloaded condition. For increasing the breaking capacity of the fuses two or more silver wire is joined in parallel with each other. These wires are adjusted in such a way so that only one wire will melt at a time. The HRC fuse is of two types In knife blade type switches the fuse wire is replaced with a live circuit with the help of fuse puller.The bolted type HRC fuses have two conducting plates which are bolted to the fuse base. This fuse requires the additional circuit for taking out the switch without getting a shock. 3) Dropout Fuse The melting of fuse causes the fuse element to drop out under gravity about its lower support. Such type of fuse is used for the protection of outdoor transformers. 4). Striker Fuse It is a mechanical device having enough force and displacement which can be used for closing tripping/indicator circuits. 5) Switch Fuse Such type of switches is used for low and medium voltages circuit. The rating of the fuse unit is in the range of 30, 60, 100, 200, 400, 600, and 800 amperes. The fuse unit is available as 3-pole and 4-pole unit. The making capacity of such type of fuses is up to 46 kA. They can safely break depending upon rating currents of the order of 3 times the load current. High Voltage HRC Fuses The main problem of the high voltage fuses is that of the corona. Therefore the high voltage fuses have the special design. They are mainly classified into three types. 1) Cartridge Type HV HRC Fuse The fuse element of the HRC fuse is wound in the shape of the helix which avoids the corona effect at the higher voltages. It has two fused elements placed parallel with each other, one of low resistance and the other is of high resistance. The low resistance wire carries the normal current which is blown out and reducing the short circuit current during the fault condition. 2) Liquid Type HV HRC Fuse Such type of fuses is filled with carbon tetrachloride and sealed at both the ends of the caps. When the fault occurs then the current, exceed beyond the permissible limit, and the fuse element is blown out. The liquid of the fuse acts as an arc extinguishing medium for the HRC fuses.They may be employed for the transformer protection and the backup protection to the circuit breaker. 3) Expulsion Type HV Fuse Expulsion type fuses are widely used for the protection of feeders and transformer because of their low cost. It is developed for 11kV, and their rupturing capacity is up to 250 MVA. Such type of fuses comprises a hollow open-ended tube made of synthetic resin-bonded paper. The fuse elements are placed in the tubes, and the ends of the tubes are connected to suitable fittings at each end. The arc producing is blown off in the inner coating of the tube, and the gases thus formed extinguish the arc. G U I DAN C E F O R I N S TALLAT I O N O F L IGHT AND FITTING PLANNING THE PROJECT 1) Check your local wiring codes and schedule inspections. 2) Decide what type of fixture will work best in the area you’re trying to illuminate. 3) Decide what kind of bulb you want for your fixture. 4) Determine voltage and current requirements for the fixture. 5) Locate a suitable power source. 6) Plan the wiring route. INSTALLING THE FIXTURE 1) Cut openings for the wiring. 2) Install the wiring. 3) Make sure your wiring is up to code. 4) Connect the devices that matches your application.