Transcription

Western Governors’ AssociationAn Introduction to Electric PowerTransmission1

An Introduction to Electric PowerTransmission – Table of Content (TOC) Glossary About Transmission Lines Electricity Generation and DeliveryTransmission Line Ownership and FundingAnatomy of a Transmission LineBuilding/Maintaining Transmission Lines Planning the System Permitting Potential Environmental Impacts Aesthetic Visual ResourcesCultural/Archeological ResourcesThreatened and Endangered SpeciesLocal Geologic FeaturesInvasive SpeciesWater ResourcesWetlandsWooded and Forested Areas2

Western Governors’ AssociationGlossary1Back to TOC

Basic Definition/Terminology Alternating Current (AC) – Electric current in which thedirection of the current's flow is reversed or alternated at60Hz in the U.S. Audible Noise (AN) – A measure in units of decibels on alogarithmic scale. Because human hearing is not equallysensitive to all frequencies of sound, certain frequencies aregiven more “weight.” Noise levels capable of being heard byhumans are measured in A-weighted decibels (dBA). Conductors (Power Lines) – Metal cables used for carryingelectric current. Corona – Electrical breakdown of the air near high voltageconductors into charged particles.4Back to TOC

Basic Definition/Terminology Current – The flow of electricity or the movement ofelectrons through a conductor typically measured in watts. Direct Current (DC) – Electric current flows continuously inthe same direction as contrasted with alternating current. Distribution Line – A line that carries electricity at lowervoltages of 12kV to 44kV and is used to distribute powerdrawn from high-voltage transmission systems to end-usecustomers. Electric & Magnetic Fields (EMF) – Invisible areas of energy,often referred to as radiation, that are associated with theuse of electric power. EMFs fall into one of two radioactivecategories – non-ionizing (low-level of radiation) or ionizing(high-level of radiation).5Back to TOC

Basic Definition/Terminology Electric Load – Electricity consumers, such as residences,businesses, and government centers that use electricity.Electric Power Transmission – The process by which largeamounts of electricity produced are transported over longdistances for eventual use by consumers.Energy – The amount of work that can be done by electricity,typically measured in kilowatt-hours (kWh) or megawatthours (MWh).Foundation – System that transfers to the ground the variousdead and live loads of the transmission structure andconductors.Generation – The production of electric energy. Fossil fuels,wind turbines, solar panels, and other technologies are usedto generate electricity.6Back to TOC

Basic Definition/Terminology Insulators – Used to contain, separate, or support electricalconductors.Interconnection – Points on a grid or network where two ormore transmission lines are connected at a substation orswitching station, or where one stage of the energy supplychain meets the next.Load Center – A particular geographical area where energy isused. Most commonly refers to an area within a utility’sservice territory where energy demand is highest (i.e., cities,major industrial areas, etc.).National Electrical Safety Code (NESC) – The NESC is the U.S.standard of the safe installation, operation, and maintenanceof electric power systems.7Back to TOC

Basic Definition/Terminology Power – Rate at which electricity does work. Measured in wattsor kilowatts (kW) or megawatts (MW).Rights-of-Way (ROW) – A legal land right, easement, set asidefor the transmission line structure and conductors needed forclearances and maintenance activities.Shield and Ground Wire – Wires used primarily for protectionfrom lightning strikes and corresponding surges.Substation – A part of an electrical transmission system thattransforms voltage from high to low, or the reverse.Switching Station – A part of an electrical transmission systemthat ties two or more electric circuits together throughswitches, to permit a circuit to be disconnected, or to changethe electric connection between circuits.8Back to TOC

Basic Definition/Terminology Transmission Line – A line that carries electricity atvoltages of 69kV or greater and is used to transmitelectric power over relatively long distances, usuallyfrom a central generating station to main substations. Transmission Structures – Used to keep high-voltageconductors (power lines) separated from theirsurroundings and from each other. Voltage – Electric “pressure” measured in volts. Powersystems are typically measured in 1,000s volts or kV. Watt – Unit of electrical power. 1MW is one millionwatts.9Back to TOC

About Transmissions LinesElectricity Generation and Delivery10Back to TOC

Electricity Generation and DeliveryElectric Operating SystemsThe National Electric Grid The U.S. electric grid is a complex interconnected system of electrictransmission lines linking generators to loads.kV115138161230345500Source: FEMA11Back to TOC

Electricity Generation and DeliveryElectric Operating SystemsThe Electric Power SystemThe diagram depicts the basicelements of an electric powersystem:Transformers at generating stationsstep the electric voltage up forefficient transport Generation – Where energy iscreated Transmission and Distribution –Energy is transported acrosshigh-voltage transmission tolower-voltage distribution lines Load – Power is delivered tohomes and businessesDistribution substations step theelectric voltage down to efficientlydeliver power to customers12Back to TOC

Electricity Generation and DeliveryInterconnections and Reliability The national grid is overseen by theFederal Energy Regulatory Commission(FERC) and the North American ElectricReliability Corporation (NERC). 3 Regional Interconnections8 Regional Entities8 Independent System Operators (ISO)4 Regional Transmission Organizations (RTO) Entities responsible for reliability ofthe national grid system: FERC, NERCRegional EntitiesUtilitiesRegional Transmission Organizations (RTOs)Independent System Organization (ISOs)Source: NERC.comSource: NERC.com13Back to TOC

Electricity Generation and DeliveryThe Western GridWestern Interconnect Bulk movement ofelectricity isaccomplished withinthree electrically separatezones: The Western Interconnect The Eastern Interconnect The Texas Interconnect The Western Interconnectis composed of 11 states,two Canadian provinces,and northern Mexico.14Back to TOC

Electricity Generation and DeliveryThe Western GridWestern Interconnect Two Federal Power MarketingAgencies (FPMAs) Bonneville Power Administration (BPA) Western Area Power Administration(WAPA) Thirty seven balancing authorities(BAs) Alternating and Direct CurrentResources Four Transmission PlanningAgencies: Columbia GridNorthern TierWest ConnectCal-ISOMap is illustrative anddoes not show alltransmission 9/wiiso.htm15Back to TOC

Electricity Generation and DeliveryThe Western GridOperational Constraints As one large machine, the WesternInterconnect must be balancedmoment to moment (frequencybased). In other words, energy that isgenerated must be consumedimmediately as there is minimalstorage in the system. Under or over supply leads todisruptions (blackouts) and thoseare reliability issues.16Back to TOC

Electricity Generation and DeliveryWhat is meant by reliability? For each of the three transmission grids theNational Electricity Reliability Corporation (NERC)defines reliability. If your lights came on, reliability was met. If a major line is lost and the system remains stable,reliability was met. If a generation source is lost and thesystem remains stable, reliabilitywas met. It is more complicated in reality, butif it is not met, the provider can befined.17Back to TOC

About Transmissions LinesTransmission Line Ownership and Funding18Back to TOC

Transmission Ownership & FundingTransmission Ownership/Funding Electric Utility – privately-held company, governmentagency, publicly owned body, or other entity that meetsthree specific criteria. Owns and/or operates facilities for provision of a servicedirectly related to electric energy provision Transmission providers fall into the following categories:1. Investor-owned utilities2. Rural cooperatives and public powerentities3. Public power authorities4. Merchant transmission providers19Back to TOC

Electricity Generation and DeliveryTransmission Ownership/Funding Investor-owned utility (IOU) – Utility owned by private investors, asopposed to rural cooperatives or public power entities. An IOU may ownboth generation and transmission and they can recover the costs of newtransmission lines through FERC-approved transmission tariffs and theirelectricity rates. Rural Cooperatives and Public Power Entities – A customerowned electric utility created to transmit and distributepower in rural areas. Rates are typically set by a board of directors elected from among thecooperative's members. Although rates are not regulated by public utility commissions, theirfacilities are subject to the same state sighting requirements asinvestor-owned utilities.20Back to TOC

Electricity Generation and DeliveryInterconnections and ReliabilityTransmission Ownership/Funding Public Power Authorities – Typically owned by a city or municipality. Not-for-profit utilityPublic Power Utilities – Owned by a city or municipality The utilities are directly accountable to the people they serve through locallyelected or appointed officials. Example: Los Angeles, San Antonio, Seattle, and Orlando operate publicly owned electricutilities Merchant Transmission Providers – Privately-owned companies that financeand own transmission facilities independent of generation developers orcustomer-serving utilities. Must take on the financial responsibility and risk associated with building a newtransmission line (unlike utilities) Costs are recouped through access charges paid by generators and/or load servingutilities21Back to TOC

Electricity Generation and DeliveryWhy do we need new transmission? Meet regulatory reliability and public policy requirements FERC 1000Public PolicyLeast CostEconomicMeet the growing need for safe, reliable electricityConnect new generation sources to the gridImprove reliability, efficiencyRenewable portfolio standards andintegrating renewablesAccess additional resources to reduce cost,diversify riskReduce congestionImprove economics22Back to TOC

About Transmissions LinesAnatomy of a Transmission Line23Back to TOC

Anatomy of a Transmission LineOverhead Transmission Line Components Shield and Ground wire – usedprimarily for protection fromlightning strikes and correspondingsurgesInsulators – used to contain,separate, or support electricalconductorsConductors – metal cables used forcarrying electric currentStructures – support structures tohold up the conductorsFoundation – system whichtransfers to the ground the variousdead and live loads of the tower andconductorsShield wireInsulatorsConductorsStructureFoundation24Back to TOC

Electricity Generation and DeliveryElectric Operating SystemsTransmission Line vs Distribution Line Transmission Line - Normallycarries electricity at voltages of69 kV or greater and is used totransmit electric power overrelatively long distances, usuallyfrom a central generatingstation to main substations. Distribution Line - Normallyconsidered to be a line thatcarries electricity at lowervoltages of 12kV to 44kV and isused to distribute power drawnfrom high-voltage transmissionsystems to end-use customers.Transmission LineDistribution Line25Back to TOC

Anatomy of a Transmission LineOverhead Transmission Line ComponentsTypes of transmission k to TOC

Anatomy of a Transmission LineOverhead Transmission Line Components Alternative Structure TypesMonopoleH-FrameSteel Lattice Factors that dictate structure types used: Size of conductor dictates load carrying capacityCompany /geographic preference or policy27Back to TOC

Anatomy of a Transmission LineOverhead Transmission Line Components Conductor alternatives Typically aluminum or copper conductors are used. Aluminum is preferred over copper for its lower costand lighter weight, however, this comes at the price ofsome energy loss that doesn't occur with copper. Aluminum Conductor Steel Reinforced (ACSR) – includessteel strands wrapped aroundaluminum conductors to addstrength. This is the most commonlyused conductor.28Back to TOC

Anatomy of a Transmission LineOverhead Transmission Line ComponentsElectrical Discharges: Corona Corona – electrical breakdown of the air nearhigh voltage conductors into charged particles. Corona can cause audible noise and radio andtelevision interference, electromagnetic interference,insulation damage, etc. Corona from transmission lines can create buzzing,humming, or crackling.29Back to TOC

Anatomy of a Transmission LineOverhead Transmission Line ComponentsElectrical Discharges: EMF Electric & Magnetic Fields (EMF) – invisible areas of energy,often referred to as radiation that are associated with theuse of electric power. EMFs fall into one of two radioactivecategories: Non-ionizing: Low-level radiation that is generally perceived asharmless to humansIonizing: High-level radiation that has the potential for cellular andDNA damageSource: Back to TOC30

Anatomy of a Transmission LineOverhead Transmission Line ComponentsElectrical Characteristics Audible Noise (AN) – is a measure in units of decibels on alogarithmic scale. Because human hearing is not equallysensitive to all frequencies of sound, certain frequencies aregiven more “weight.” Noise levels capable of being heard byhumans are measure