Wiring Materials and Overcurrent Protection PDF

WIRING MATERIALS and OVERCURRENT PROTECTION PEC CHAPTER 2 / 3 1  Wiring Materials and Overcurrent Protection Wires An electrical conductor is any material that conducts electrical current. A wire is a common electrical conductor. Most conductors used i...

WIRING MATERIALS and OVERCURRENT PROTECTION PEC CHAPTER 2 / 3 1  Wiring Materials and Overcurrent Protection Wires An electrical conductor is any material that conducts electrical current. A wire is a common electrical conductor. Most conductors used in building applications are classified according to a wire gauge standard and on cross-sectional area of the wire. Cross sectional area in unit is called circular mils. A mil is equal to 1/1000 inch, so one circular mill (cmil) is equal to the cross-sectional area of a 0.001 in diameter circle. Silver is the best electrical conductor because it has the least resistance of common material. Gold is also an excellent conductor. To compromise between good conductivity and economy, copper and/or aluminum conductors are used are used in building constructions/installations. As conductor material, aluminum has significant weight and cost advantages over copper. However, copper conducts electricity better than aluminum. 2  Wiring Materials and Overcurrent Protection Wires Conductor Ampacity A conductor ampacity is the maximum current (in amperes) it can carry continuously without exceeding the temperature limitations of the insulation and sheathing material. Simply, it is the conductor’s maximum current carrying capacity based on: Wire thickness Type of conductor material Insulation and sheathing type Temperature and exposure 3  Wiring Materials and Overcurrent Protection Ampacity Tables 4  Wiring Materials and Overcurrent Protection Wires Silver and Gold – are excellent conductors but both are too costly just for wiring installations. Copper and Aluminum – as a compromise between good conductivity and economy are used for wiring installations. Copper vs Aluminum – Aluminum is lighter and cost less compared to copper, while copper has lower resistance and stronger compared to aluminum. Copper clad aluminum – Aluminum wire with a thin coating of copper. https://www.shanpowercable.com/photo/pl12314999- 0_6_1kv_single_phase_armoured_electrical_cable_copper_ aluminum_xlpe_pvc_awa_sta_electric_power_cable.jpg 5  Wiring Materials and Overcurrent Protection Wires Conductor insulation – provides electrical isolation and some physical protection to the conductor. Prevents loss of power and short circuits. Different types of insulation are used in conductors depending on the environment in which it can be used, (indoor, outdoor, overhead, underground, low voltage, high voltage, low temperature, high temperature, dry, damped or wet locations). 6  Wiring Materials and Overcurrent Protection Wires Jacket – applied over insulation to provide additional chemical, physical, or thermal protection to the conductor and its insulation. Plastic – is the widely used insulation. Cloth and rubber – insulation used in old conductors. https://instrumentationtools.com/wp- content/uploads/2016/04/instrumentationtools.com_i nsulating-material-for-cable-requirements.jpg 7  Wiring Materials and Overcurrent Protection Wires Conductor Insulation and Material Designations and Markings Table 18.10 Conductor Insulation and Material Designations and Markings A – Glass fiber or similar insulation X – Cross-linked synthetic material (formerly asbestos, w/c is polymer (plastic) insulation obsolete) Z – Modified FEP – Fluorinated ethylene tetrafluoroethylene insulation propylene insulation L – Lead sheathed -2 – 1940F (900C) and wet or dry N – Nylon jacketed H – Heat resistant: up to 1670F (750C) PF – Perfluoroalkooxy insulation R – Thermoset insulation (e.g., HH – Extra heat resistant: up to rubber or synthetic rubber) 1940F (900C) S – Silicone (thermoset) insulation W – Moisture resistant T – Thermoplastic insulation 8  Wiring Materials and Overcurrent Protection Wires Conductor Insulation and Material Designations and Markings RHH – Thermoset (e.g., rubber or synthetic THW – Thermoplastic. 1670F (750C) rubber). 1940F (900C) temperature rating. Extra temperature rating. Heat resistant. Wet and heat resistant. Not moisture resistant (not suitable dry rating. Not sunlight resistant. for conduits exposed to weather). Not sunlight resistant. THW-2 – Thermoplastic. 1940F (900C) RHW – Thermoset (e.g., rubber or synthetic temperature rating. Extra heat resistant. Wet rubber). 1670F (750C) temperature rating. and dry rating. Not sunlight resistant. Moisture and heat resistant. Not sunlight resistant. TWHN – Thermoplastic. 1670F (750C) RHW-2 – Thermoset (e.g., rubber or synthetic temperature rating. Moisture and heat rubber). 1940F (900C) temperature rating. Extra resistant. Nylon jacket over insulation (slides heat resistant. Not sunlight resistant. through conduit easier). Not sunlight THHN – Thermoplastic. 1940F (900C) temperature resistant. rating. Extra heat resistant. Not moisture resistant (not suitable for conduits exposed to weather). TWHN-2 – Thermoplastic. 1940F (900C) Nylon jacket over insulation (slides through temperature rating. Moisture and extra heat conduit easier). Not sunlight resistant. resistant. Nylon jacket over insulation (slides through conduit easier). Not sunlight resistant. XHHW-2 – Thermoset (e.g., cross-linked synthetic polymer). 1940F (900C) temperature 9 rating. Extra heat resistant. Wet and dry rating.  Wiring Materials and Overcurrent Protection Corrections Factors 10  Wiring Materials and Overcurrent Protection 3.10.3.3 Conductors. (A) Minimum Size of Conductors. The minimum size of conductors shall be as shown in Table 3.10.3.3 (A), except as permitted elsewhere in this Code 11  Wiring Materials and Methods Example 1. Determine the size of wire for a three phase load that consumes 175A 3Phase Load 175A Continuous Ampacity of wire : I = 175A X 1.25 = 218.75A Article 4.30.2.2 Single Motor. Conductors that supply a single motor in a continuous duty application shall have an ampacity of not less than 125 percent of the motor full-load current rating, as determined by 4.30.1.6(A)(1), or not less than 4.30.2.2(A) through (G). 12  Wiring Materials and Methods Example 1. Determine the size of wire for a three phase load that consumes 175A 3Phase Load 175A Determine the size of wire : I = 175A X 1.25 = 218.75A Continuous 13  Wiring Materials and Methods Example 1. Determine the size of wire for a three phase load that consumes 175A 3Phase Load 175A Continuous Determine the size of wire : I = 175A X 1.25 = 218.75A Use 3 – 100mm2 THHW + 1 – 30mm2 THW in 2” diam IMC 14 Wiring Materials and Overcurrent Protection Article 4.30.2.2 Single Motor. Conductors that supply a single motor in a continuous duty application shall have an ampacity of not less than 125 percent of the motor full- load current rating, as determined by 4.30.1.6(A)(1), or not less than 4.30.2.2(A) through (G). 15  Wiring Materials and Methods Example 2. Determine the size of wire for a three phase motor with the following ratings: 22kW, 460V, FLA= 43A Note: If FLA is not given, use the FLA in Table 4.30.14.4 of PEC 2017. Or compute FLA based on 80% efficiency, and 80% PF. Determine the size of wire : I = 43A X 1.25 = 53.75A Use 3 - 14mm2 THHW + 1 – 8mm2 THW in ½” dia IMC 16  Wiring Materials and Methods Example 3. Determine the size of wire for each three phase motor shown below, and the size of the feeder wire. All motors are 3PH 460V. Use the FLA given in Table 4.30.14.4 22kW FLA = 40A 3 - 8mm2 THHW + 1 – 8mm2 THW in ½” dia IMC 37.5kW FLA = 65A 3 - 22mm2 THHW + 1 – 8mm2 THW in 1” dia IMC 55kW FLA = 96A 3 - 50mm2 THHW + 1 – 14mm2 THW in 1-1/2” dia IMC Feeder wire size : I = ( 40A + 65 + 96 ) + ( 96 X 0.25) = 225A Use 3 - 100mm2 THHN + 1 – 30mm2 THW in 2” dia IMC 17  Wiring Materials and Methods Raceway Raceway – is an enclosed channel such as conduit, tube, or gutter designed for holding wires, cables, or busbars. https://2.imimg.com/data2/JI/QG/MY-3241872/cable-tray-raceways-250x250.jpg https://lh3.googleusercontent.com/proxy/UJi1g0Ls21BNSFMrYn6gDkBzxAtY0oiOHvQyKIdzLpS2mB4b5WwG_VDo- rmi2ze6heIy5aW7iQeIcW_K256rMipaLa4b6tenxassuD_80FXxx5wsa1Rzgx0iB7vevJpfmSfmx4WPeklPR90MCNJ4AQ3EbsfROoRHAaxv5YWWj_P2rMlGEI4cYMqj8u_p https://lh3.googleusercontent.com/proxy/UJhEV3_tCNPg9PijOiSMosxgpJqxvPsPU_1HtQIdfrQHMIOhKOfgkACxMF8Lj3xWHPqYb- o9LF0VqUHReqBDJIKque61b88JRDt9vSxhhp0_CahGGek3flOThwAQ0o07klC9Nso 18  Wiring Materials and Methods Raceway Rigid metal conduit (RMC) – is a heavy galvanized steel or aluminum tube that looks like the galvanized steel pipe used for plumbing applications except it is much smoother. Intermediate metal conduit (IMC) – is a galvanized steel or aluminum tube that has a thinner wall than rigid metal conduit. Electrical metallic tubing (EMT) – is a thin- walled galvanized steel or aluminum tube in nominal diameters up to 4 inches. Electrical nonmetallic tubing (ENT) – is a Rigid nonmetallic conduit – is a thin- walled pipe of polyvinyl chloride (PVC). flame-retardant corrugated plastic tube that is semiflexible such that it can be bent Flexible metal conduit – is similar to by hand. armored cable, but it is installed without cables or wiring in it. 19  Wiring Materials and Methods Raceway Miller, C. R. (2015). Illustrated Guide to the National Electrical Code: Based on the 2014 National Electrical Code-6th Edition. 20  Wiring Materials and Methods PVC 3.52.1.2 Rigid Polyvinyl Chloride Conduit (PVC). A rigid non metallic raceway of circular section, with integral or associated couplings, connectors, and fittings for the installation of electrical conductors and cables. 3.52.2 Installation 3.52.3 Uses not permitted A. Concealed A. Hazardous (Classified ) Locations B. Corrosive Influences. B. Support of luminaires C. Cinders C. Physical Damaged D. Wet Locations D. Ambient Temperature (in excess of E. Dry and Damp Location 50deg C F. Exposed (Schedule 80) E. Theaters and Similar Locations G. Underground installation 21  Wiring Materials and Methods PVC 3.52.2.11 Size (A) Minimum. PVC Conduit smaller than metric designator 16 (trade size ½) shall not be used. (B) Maximum. PVC conduit larger than metric designator 155 (trade size 6) shall not be used. 3.52.2.13 Number of conductors. The number of conductors shall not exceed that permitted by the percentage fill specified in Table 10.1.1.1 3.52.2.15 Bends – How Made. Bends shall be so made that the conduit will not be damaged and the internal diameter of the conduit will not be effectively reduced. Field bends shall be made only with identified bending equipment. The radius of the curve to the centerline of such bends shall not be less than that shown in Table 10.1.1.2 22  Wiring Materials and Methods PVC 23  Wiring Materials and Methods PVC R * 90deg bends are commercially available * Bends can be done at site using torch 3.52.2.17 Bends - Number in One Run. There shall not be more than the equivalent of four quarter bends (360deg total) between pull points, for example conduit bodies and boxes. 24 Wiring Materials and Methods 25 Wiring Materials and Overcurrent Protection 26 Wiring Materials and Methods 27  Wiring Materials and Methods RIGID METAL CONDUIT (RMC) 3.44.1.2 Definition Rigid Metal Conduit (RMC). A threadable raceway of circular cross section designed for the physical protection and routing of conductors and cables and for use as an equipment grounding conductor when installed with its integral or associated coupling and appropriate fittings. 3.44.2.1 Uses permitted A. Atmospheric Conditions and Occupancies 1) Galvanized Steel and Stainless Steel RMC 2) Red Brass RMC 3) Aluminum RMC 4) Ferrous Raceways and Fittings B. Corrosive environments. 1) Galvanized Steel, Stainless Steel, and Red Brass RMC, Elbows, Couplings and Fittings. 2) Supplementary Protection for Aluminum RMC. C. Cinder Fill. Galvanized steel, stainless steel, and red brass RMC shall be permitted….. D. Wet Locations. All supports, bolts, straps, screws, and so forth, shall be corrosion resistance materials or protected against corrosion by corrosion resistant material. 28 Wiring Materials and Methods 29 Wiring Materials and Methods 30  Wiring Materials and Methods RMC R * 90deg bends are commercially available * Bends can be done at site using hydraulic bender 3.44.2.17 Bends - Number in One Run. There shall not be more than the equivalent of four quarter bends (360deg total) between pull points, for example conduit bodies and boxes. 31 Wiring Materials and Methods 32 Wiring Materials and Methods 33  Wiring Materials and Overcurrent Protection Overcurrent Protection Device Art 2.40.1.2 Current-Limiting Overcurrent Protective Device. A device that, when interrupting currents in its current-limiting range, reduces the current flowing in the faulted circuit to a magnitude substantially less than that obtainable in the same circuit if the device were replaced with a solid conductor having comparable impedance. Circuit Breaker A mechanical switching device, capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time, and breaking currents under specified abnormal circuit conditions such as those of short circuit. 34  Wiring Materials and Overcurrent Protection Current-limiting Circuit Breaker A circuit breaker with a break-time short enough to prevent the short-circuit current reaching its attainable peak value. 35  Wiring Materials and Overcurrent Protection Plug-in Circuit Breaker A circuit breaker which, in addition to its interrupting contacts, has a set of contacts which enable the circuit breaker to be removed. Withdrawable Circuit Breaker A circuit breaker which, in addition to its interrupting contacts, has a set of isolating contacts which enable the circuit breaker to be disconnected from the main circuit, in the withdrawn position, to achieve an isolating distance in accordance with specified requirements. 36  Wiring Materials and Overcurrent Protection Moulded-case Circuit Breaker A circuit breaker having a supporting housing of moulded insulating material forming an integral part of the circuit breaker. Disconnector A mechanical switching device, which in the open position, complies with the requirements specified for isolating function. Release A device, mechanically connected to a mechanical switching device, which releases the holding means and permits the opening or the closing of the switching device. 37  Wiring Materials and Overcurrent Protection Fault types and currents Overload Operating conditions in an electrically undamaged circuit which causes an overcurrent. Short-circuit The accidental or intentional connection by a relatively low resistance or impedance, of two or more points in a circuit which are normally at different voltages. Residual current (I∆) It is the vectorial sum of the currents flowing in the main circuit of the circuit breaker. 38 Wiring Materials and Overcurrent Protection 39 Wiring Materials and Overcurrent Protection 40  Wiring Materials and Overcurrent Protection Rated performances Rated operational voltage (Ue) A rated operational voltage of an equipment is a value of voltage which, combined with a rated operational, determines the application of the equipment and to which the relevant tests and the utilization categories are referred to. Rated insulation voltage (Ui) The rated insulation voltage of an equipment is the value of voltage to which dielectric tests voltage and creepage distance3s are referred. In no case the maximum value of the rated operational voltage shall exceed that of the rated insulation voltage. 41  Wiring Materials and Overcurrent Protection Rated performances Rated impulse withstand voltage (Uimp) The peak value of an impulse voltage of prescribed form and polarity which the equipment is capable of withstanding without failure under specified conditions of tests and to which the values of clearances are referred. Rated frequency The supply frequency for which an equipment is designed and to which the other characteristic values corresponds. 42  Wiring Materials and Overcurrent Protection Rated performances Rated uninterrupted current (In) The rated uninterrupted current for a circuit breaker is a value of current, that the circuit breaker can carry during uninterrupted service. Rated residual operating current (I∆n) It is the rms value of a sinusoidal operating current assigned to the CBR by the manufacturer, at which the CBR shall operate under specified conditions. 43  Wiring Materials and Overcurrent Protection Performance under short circuit condition Rated making capacity The rated making capacity of an equipment is a value of current, stated by the manufacturer, which the equipment can satisfactorily make under specified making conditions. Rated breaking capacity The rated breaking capacity of an equipment is a value of current, stated by the manufacturer, which the equipment can satisfactorily break, under specified breaking conditions. 44  Wiring Materials and Overcurrent Protection Performance under short circuit condition Rated ultimate short-circuit breaking capacity (Icu) The rated ultimate short-circuit breaking capacity of a circuit breaker is the maximum short-circuit current value which the circuit breaker can break twice ( in accordance with the sequence O-t-CO), at the corresponding rated operational voltage. After the opening and closing sequence, the circuit breaker is not required to carry its rated current. 45  Wiring Materials and Overcurrent Protection Performance under short circuit condition Rated service short-circuit breaking capacity (Ics) The rated service short-circuit breaking capacity of a circuit breaker is the maximum short-circuit current value which the circuit breaker can break three times in accordance with the sequence opening and closing operations (O-t-CO-t-CO), at a defined rated operational voltage and at a defined power factor. After this sequence, the circuit breaker is not required to carry its rated current. 46  Wiring Materials and Overcurrent Protection Performance under short circuit condition Rated short-time withstand current (Icw) The rated short-time withstand current is the current that the circuit breaker in the closed position can carry during a specified short time under prescribed conditions of use and behaviour; the circuit breaker shall be able to carry this current during the associated short-time delay in order to ensure discrimination between the circuit breakers in series. 47  Wiring Materials and Overcurrent Protection Performance under short circuit condition Rated short-circuit making capacity (Icm) The rated short-circuit making capacity of an equipment is the value of short circuit making capacity assigned to that equipment by the manufacturer for the rated operational voltage, at rated frequency, and at specified power factor for ac. 48 Wiring Materials and Overcurrent Protection Time current curves 49 Wiring Materials and Overcurrent Protection Protection Coordination 50 Wiring Materials and Overcurrent Protection Protection Coordination 51 Wiring Materials and Overcurrent Protection 52