R531 Study Guide Power PDF

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Power Unit study guide...

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ARCH 531 Power Exam Study Guide

 Renewable Energies ▪

Electric power distribution o

Electricity: AC and DC Direct Current (DC)

Alternating Current (AC)

- Constant current flow, voltage, and direction - Can be stored in batteries - Delivered from plant to consumer with high current - Can be delivered only short distance - Used for special applications (e.g. elevators)

- Varying current and voltage flow and direction - Cannot be stored in batteries - Delivered from plant to consumer with low current and high voltage - Can be delivered 100s of miles away - Most of today’s electricity

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**Direct current has constant current flow and voltage: TRUE **The overriding design objective for any electric power distribution system is: SAFETY o Frequency: the number of cycles of alternating voltage or current per second ▪ Frequency must match equipment to correct frequency → if not, equipment will overheat/burn out/decrease battery life World energy use/outlook: general understanding o U.S. were leaders in energy consumption and carbon dioxide emissions until around 2011 when China became the new leaders Buildings’ role in energy/electricity consumption o Buildings are responsible for about 50% of the U.S.’s energy consumption Environmental Performance Index (EPI) slides will not be on exam Wind energy o #2 renewable energy source o Ways to collect wind energy: ▪ Wind farms (onshore, offshore) • Individual turbines are clustered into strings • All connected to each other underground feeding to the generator • Spread out so turbulent flow does not interfere → makes less efficient •

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i.e. Flint Hills: prime location, wind all year round, multiple transmission lines available Wind turbines • • •

Need >8 mph to work Up to a football field in rotor size Concern with birds: tend to change flight route 300-600’ before turbines; might affect migration patterns

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Noise concern: noise could have a negative impact on wildlife •

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Solar energy

Farther you move away, sounds drops significantly

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Photovoltaics - solar panels - the conversion of light into electricity using semiconducting materials ▪ Mounting options 

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• Fixed tilt  • Single axis tracking • Dual axis tracking 3 design factors that should be taken into consideration when designing for roof mounted photovoltaic panels • • •

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Shading factors Roof drain location Roof membrane type

Biomass energy o Biomass includes: wood, biogas/landfill gas, biodiesel/ethanol o Typically 0.1-75 MW o Can be low cost o Available almost anywhere **In typical power plant ⅔ of power is lost from generation site to end facility Geothermal o o

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Heat being generated from the earth’s core Dry steam power plant ▪ [Plants pipes create existing steam in the ground through a turbine to generate electricity o Flash steam power plant ▪ Hot water is vaporized through pressure to turn a turbine o Binary cycle power plant ▪ Two different liquids one gets heated and one gets vaporized to turn a turbine Co/tri-generation: microturbines o

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Cogeneration (CHP): ▪ Uses waste heat from power generation to produce thermal energy • i.e. simultaneous production of electricity and heat from one fuel source ▪ 50-75% of electric efficiency compared to average 33% of fossil fuel powered plants Trigeneration (CCHP): ▪ Combined heating, cooling, and power ▪ Uses absorption chillers to turn waste heat into chilled water ▪ Up to 50% greater efficiency than similar cogeneration plant Microturbines ▪ Type of combustion turbine that produces both heat and electricity on a relatively small scale ▪

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Offer several potential advantages compared to other technologies for small-scale power generation, including: a small number of moving parts, compact size, lightweight, greater efficiency, lower emissions, lower electricity costs, and opportunities to utilize waste fuels

Wave/tidal energy o Pelmis ▪ Wave-energy converter ▪ Hydromotors drive electrical generators to produce electricity → power is

fed to the seabed via a single dynamic umbilical connected to a transformer in the machine’s nose ▪ ▪

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**Most successful wave-energy converter to date Basically there is a power plant on shore with cords connecting the converter = travel of electricity Oyster wave ▪ Wave-energy converter ▪ Uses drive technology to drive water to generator (hydroelectric power conversion plant) on site via high pressure flow line CETO ▪ Wave-energy converter ▪ High pressure hydraulic “balloons” move up/down in water ▪ Transfers energy to hydroelectric power conversion plant Water Turbine ▪ Wave-energy converter ▪ Submerged “wind” turbine that collects energy from waves ▪ Converter underneath turbine → converts energy on the spot (unlike others)

Electrical Systems ▪ Equipment o

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Substations ▪ Genergates, transmits and distributes electricity ▪ Transforms from high to low or low to high Service entrance

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Overhead and underground service **Which means of service delivery is typically more expensive to install: UNDERGROUND SERVICE Transformer ▪ Step up/step down - changing the voltage level ▪ Cooling methods • Dry - air • Wet - oil ▪ Locations • Dry - inside or outside • Wet - inside (in a vault) or outside ▪ **An indoor operating transformer gives off heat but the electrical room does not require natural or mechanical cooling: FALSE ▪

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**When placed inside a building, oil-filled transformers must be placed inside a transformer vault: TRUE

▪ **Transformers can be specified for both indoor and outdoor use: TRUE Meter, smart meter ▪ Electric meters are installed and controlled by the utility company to measure the amount of electric power used in a building • This is how the power company knows how much to bill its customers • The meter is either placed outside or inside the building • If inside, must be accessible to utility personnel for reading • Meter reading are mostly done remotely ▪ **An office building with multiple tenants only needs one meter: FALSE Switch ▪ A switch is a device to bridge or break the flow of electricity • Like a wall light switch but much bigger • Electronic switches are used in the building automation, automated energy management systems • Set on timer to turn on and off equipment to conserve energy ▪ Main switch • Also known as service disconnect, service switch, main disconnect, main breaker • Purpose is to bridge, break, or disconnect the flow of all electricity to the building, except emergency equipment for fire and safety or for major electrical repairs Fuses and circuit breakers ▪ Fuses and circuit breakers are circuit protection devices • These devices are designed to disconnect a circuit automatically whenever the current reaches a predetermined value that would cause a dangerously excessive temperature in the conductor • Purpose is to protect electrical equipment ▪ Fuses • One-time use (blow) ▪ Circuit breakers • Most widely used overcurrent protection device • Function like a fuse but is reusable (trip)

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Can also act as a switch

Plug loads ▪ Any application or equipment that uses an electrical outlet or plug Panelboard ▪ Panelboard or electrical panel accepts a relatively large block of power and distributes it in smaller blocks to different circuits • Fuses and circuit breakers are generally included in the panel ▪ Panels are either surface mounted or recessed flush with the finish wall surface Switchboard/switchgear ▪ Switchboard or switchgear is essentially a larger version of a panelboard • Fuses or circuit breakers and meters are generally included in the assembly ▪ Switchgear is the same as switchboard but for high-voltage (above 600 V) service ▪ Generally located in a well-ventilated “electrical switchgear” room designated for that purpose ▪ **A switchboard typically contains: SWITCHES, FUSES/CIRCUIT BREAKERS/METERS Unit substation ▪ It is a single package combining a step-down transformer with complete switchboard and meter(s) • Economical due to prefabricated construction • Indoor and outdoor use Uninterruptible power supply (UPS) ▪ UPS provides uninterrupted power for a short period of time for backing up data or waiting until on-site generators go online as emergency power. ▪ UPS is battery based Emergency standby power: generators? ▪ **In the event of a power outage, a hospital should have which of the following? UNINTERRUPTIBLE POWER SUPPLY (UPS) & ONSITE POWER GENERATOR

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Wiring and Raceways o

Conducting materials ▪ Copper - excellent conductor of heat and electricity ▪ Aluminum - lighter and cheaper than copper

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Conductor sizes ▪ American Wire Gauge (AWG) • AWG is preceded by a number which indicates size of wire • e.g. 14 AWG or 16 AWG • As AWG number increases, size of wire decreases • e.g. 10 AWG is bigger/heavier than 14 AWG • No. 8 AWG and smaller (diameter) are called wire • No. 6 AWG and larger (diameter) are called cable • Two or more wires assembled together is also a cable • No. 0000 AWG (No. 4/0 AWG) is the largest AWG designation • All cable is made up of wires • Note: 8, 10, and 12 AWG available as both wire and cable

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• **A 4 AWG conductor is considered a wire → FALSE Thousand Circular Mil (Kcmil)

Conductor types ▪ **Conductor ‘ampacity’ is determined by: MAX SAFE OPERATING TEMPERATURE OF THE CONDUCTOR Temperature rating and limitations Location definitions ▪ Dry - house being built ▪ Damp - basement ▪ Wet - car wash Allowable ampacity ▪ Maximum amount of amps that can go through a wire Principal determinants of conductor operating temperature: ▪ Ambient temperature ▪ Heat generated internally in the conductor as the result of load current flow ▪ Rate at which the generated heat dissipates ▪ Adjacent load-carrying conductors (adjacent conductors have the dual effect of raising the ambient temperature and impeding heat dissipation) Cable types: a general understanding ▪

Armored Cable: Type AC • •

Commonly referred to as flexible armored cable Trade name is BX cable

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It is manufactured in two, three, and four wire assemblies with insulated wires wrapped with a spiral-wound interlocking metal jacket Type AC is restricted to dry locations

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Metal Clad Cable: Type MC • •

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Another type of flexible armored cable (BX cable) With additional PVC jacket is suitable for wet locations

Non-metallic Sheathed Cable • •

Trade name is Romex Outer jacket is typically made of rubber or plastic •

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The jacker is flame-retardant and moisture resistant for all three types

• Restricted to residential or other small structures Non-metallic Sheathed Cable Type NM •

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Non-metallic sheathed cable that is intended to be used where protected from physical damage Non-metallic Sheathed Cable Type NMC •

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Corrosion and fungus resistant cable that is intended to be used where exposed to fumes, vapors, and liquids such as ammonia and barnyard acids in dairy barns and similar barn buildings

Non-metallic Sheathed Cable Type NMS •

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Hybrid cable consisting of power, communications, and signaling conductors under one jacket Flat Cable: Type FCC •

Also known as under-carpet cable

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Flat cable assemblies consist of 2, 3, 4, or 5 parallel conductors of 10 AWG special stranded copper wires

Mineral-insulated, Metal Sheathed Cable: Type MI •

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A factory assembly of one or more conductors insulated with a highly compressed refractory mineral insulation and enclosed in a liquid-tight and gas-tight continuous copper or alloy steel sheath • Can be used in a dry or wet location, indoors or outdoors and in hazardous areas Underground Feeder and Branch-Circuit Cable: Type UF •

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A factory assembly of one or more insulated conductors with an integral or an overall covering of nonmetallic material suitable for direct burial in the earth

Service-entrance Cable: Type SE and USE •

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A single conductor or multiconductor assembly provided with or without an overall covering, primarily used for services • Type SE has a flame-retardant and moisture-resistant covering • Type USE is for underground use and has a moisture-resistant covering but not required to have a flame-retardant covering ▪ **When connecting to vibrating equipment in a dry location, what is the appropriate type of conduit? FLEXIBLE METAL CONDUIT ▪ **Riser shafts fulfill the following purpose: VERTICALLY CARRYING CABLES FROM THE EQUIPMENT ROOM TO EACH FLOOR Raceways: purpose and types ▪ Any channel expressly designed for holding wires/cables ▪ Types of raceways: conduits, wireways, surface raceways, cable trays, floor raceways, ceiling raceways, busways, cablebus ▪ Metal conduits: used for straight runs and for connection to equpment that is noise and vibration free ▪ Flexible Metal Conduit: Type FMC ▪ **Which type of floor raceway is the most flexible? ACCESS FLOOR ▪ **Functions of raceways: • Provide means for distributing wires • Physically protect wires • Provide a grounded enclosure (in the case of metal conduit) • Protect the surroundings against the effects of a fault in the wiring

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Calculations o

Terminology ▪ Conductor - any substance that allows energy/electricity to flow through it ▪ Insulator - any substance that does not allow energy/electricity to flow through it ▪ Circuit - a closed path through which current/electricity flows from source of electricity and back to the source ▪ Current - the rate at which electricity flows (amps) ▪ Voltage - the pressure at which the electricity flows ▪ Resistance - measured in ohms (Ω) is the resistance / impedance to the flow of current by a piece of material / conductor

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Power

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Measured in watts (W) is defined as the rate of doing work (amount of electricity consumption) • Power = Voltage x Current (P = VI or W = VI)  • For power equipment running on alternating current:  • Power = Voltage x Current x Power Factor (W = VI x pf) • Note: when calculating power for QAC power equipment, you must include power factor (pf)

Feeder ▪ A circuit, such as conductors in conduit or a busway run, that carries a large block of power from the service equipment to a subpanel, a branch-circuit panel, or to some point at which the block or power is broken down into smaller circuits ▪ i.e. like the main trunk of a tree Branch circuits ▪ That portion of a wiring system extending beyond the final over-current device protecting a circuit (i.e. beyond the circuit breaker, panelboard) ▪ i.e. like the branches of a tree leading to the leaves Total resistance: series and parallel circuits Relationship between voltage, current, and resistance Horsepower Power factor ▪ Power Factor (pf): only applies to power equipment running on alternating current (AC) when calculating power ▪ (W) W = VI * pf  ▪ Impedance (Z) causes a phase difference between current and voltage  • The difference is described as power factor and it causes a reduction in percentage of power used ▪ If pf is not used, the product of voltage and current is known as volt-amperes • Volt-amperes (VA) is important for sizing equipment. For AC only.  ▪ Equipment with high pf is more efficient than equipment with low pf ▪ **Equipment rated with a high power factor (closer to 1) is better than equipment rated with a low power factor: TRUE

 Energy ▪ Energy = Power*Time = W*hr  ▪ Electrical energy is usually measured in watt-hours but is most commonly measured in thousands of watt-hours, or kilowatthours (kWh) ▪ kW = W / 1000

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Voltage drop ▪ Conductors have a voltage rating (e.g. 300 V, 600 V, etc.)  • The voltage applied to a conductor should be equal to or less than the voltage rating of the conductor ▪ With distance, voltage drops across the length of a conductor • If necessary, NEC requires you to increase conductor size to accommodate voltage loss ▪ Conductors should be designed for:  • Voltage drop not to exceed 3% of power requirement on a branch circuit • Maximum total voltage drop for a combination of branch circuit and feeder not to exceed 5% ▪ To obtain the percentage of a voltage drop:

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National Electrical Code (NEC) ▪ NEC requires you to increase conductor size to accommodate voltage loss **Ohm’s Law establishes the relationship between: VOLTAGE/CURRENT/RESISTANCE

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Signal Systems o

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Access systems ▪ Key card access • Proximity / contactless • Swipe / magnetic • Smart card • Personal data / preferences Vertical and horizontal distribution ▪ Vertical Distribution • Centralized vs distributed • Stack telecommunication closets/rooms

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 Horizontal Distribution • Surface Raceways  • Cable Trays  • Floor Raceways  • Cellular floor  • Raised/access floor • Fixed height, low profile  • Adjustable height  • Poke-through  • Ceiling Raceways

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▪ Distribution methods Building automation Micro-Electro Mechanical Systems (MEMS) ▪ An intelligent system-on-a-chip **An acoustic detector will produce an alarm when: A SPECIFIC RANGE OF FREQUENCIES IS DETECTED...