Grounding Bonding for Substation Communications

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GROUNDING BONDING FOR SUBSTATION COMMUNICATIONS

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  • PRESENTATION TO IEEE PES, ORLANDO CHAPTER:

    GROUNDING & BONDING CONSIDERATIONS FOR SUBSTATION COMMUNICATIONS AND SMART GRIDDeveloped and Presented By:Adrian G Zvarych, PEPrincipal EngineerTRC EngineeringMember, IEEE24 September 2009azvarych@trcsolutions.com Additional Contributions & Peer Review By: Michael Cunningham, Senior Engineer - TRC

  • Class ObjectivesUnderstand Substation Grounding/Bonding Design Goals to Satisfy Communications RequirementsReview of Typical Substation Control House Grounding/Bonding PracticesReview Typical Telecom Room Grounding/Bonding PracticesNecessary Grounding & Bonding Elements for a Smart Grid Friendly and Communications Ready Substation Control HouseLook-Ahead for other opportunitiesReview

    40Years of Service19692009

  • Change Has Been Happening40Years of Service19692009

  • Part 1: Substation Communications EvolutionCommunications migration path:Analog to digitalDiscrete to multiplexedLocal Information decision needs to remote and diverse needsLower Reliability to High Reliability (design and need)Minimal regulation (self- on inter-industry regulation to increased scrutiny and regulation by others)40Years of Service19692009

  • Pilot Wire Interface& Isolation Transformers

  • Circa 1900s Distribution Breakers1912 Manufactured GE Oil Break SwitchSTILL IN SERVICE!!!!

  • Legacy Substation Communications SystemsPEOPLE/OPERATIONSStation Operators with all local indicationCommunications to Control Center via Power Line Carrier or Telephone Company Copper Circuits (SCADA)Radio Dispatch for Crews

    RELAY PROTECTIONPower Line Carrier (first digital form of substation communications ON-OFF)Copper Based Pilot WireAll analog meters and electromechanical relaysNeeds driven by electric utility operations & reliability

    40Years of Service19692009

  • Advancements in Legacy Substation Relaying and CommunicationsDriven by build out of high voltage and EHV transmission gridNeed for high speed and reliable/secure relayingNeed for remote and central monitoring and control of station equipmentFirst discrete component solid state relaying deployed in substations in the 1970sSingle Side-Band Power Line Carrier more channels, more functionalityAnalog Point-To-Point MicrowaveOptical Networks40Years of Service19692009

  • Development of Non-Copper Substation Communications SystemsAnalog Microwave (circa 1960s)Digital Microwave (circa 1980s)Spread Spectrum 900MHz (circa 1980s)Fiber (circa 1990s)40Years of Service19692009

  • Advancements of Components/TechnologyProtective RelayingElectromechanical Relays Solid State RelaysSolid State Relays Microprocessor Relays

    CommunicationsCopperAnalog MicrowaveDigital Microwave900MHz Licensed & Spread Spectrum/UnlicensedFiberDiscrete Analog Digital Multiplexed IP40Years of Service19692009

  • TELECOMMUNICATIONS CIRCUIT HIERARCHYDWDM 1246722,0168,06432,256129,024ooPhone linesper circuit type

  • And Now Smart Grid!

  • Effects of Smart Grid and Communications TechnologyHigher density of low-signal voltage circuits (RS-232, RS-485) over copper in the control houseMore fiber in the control houseMore non-substation hardened devices entering the control houseIT-Telecom teams becoming more involved in substation control housesOrganizational awareness of substation environment vs data center/telecom room requirements

    40Years of Service19692009

  • Users of Substation InformationSystem OperatorsP&C EngineeringAsset ManagementCustomer Service CenterField Maintenance Personnel (line trucks, P&C, substation, etc.)Electric System Customers (indirectly)Personnel ManagersCorporate Security (access management, surveillance)IT-Security Cyber-Security TeamsUtility Interchange (Where Transmission Tammy draws the line)Others40Years of Service19692009

  • Substation Communications: Change Is HereTraditionalTelemetry Watts, Vars, Volts, AmpsStatus Open, Closed, Major, MinorControl Open, Close, Raise, LowerVoiceSCADA Analog/4 Wire AC Data

    Present DayAll of the above, plusTemperature Outdoor Ambient, Control HouseTransformer Telemetry Winding Temps, Dissolved Gas, Tap PositionBattery VoltageIP ServicesSecurity Surveillance, Door Access ControlHigh Speed Remote Access for IEDsSyncrophasorsLocal Employee LAN AccessSCADA

    40Years of Service19692009

  • Change Is HereIncreased data flow (to 27 TB/day or higher in larger utility systems) from substationsNot just SCADANon-Traditional organizations using or managing substation systems and informationIncreased deployment of non-station hardened equipment, despite efforts by IEEE to develop standards such as IEEE-1613

    40Years of Service19692009

  • PART 2: NAVIGATING THE TRANSITIONGOALS OF GROUNDING/BONDING SUBSTATION AND TELECOMBASICS AND DEFINITIONSREAL WORLD CASE STUDY

  • Substation GoalsSafetyStep and TouchGround Potential RiseReliabilityLightning Mast/ShieldingMinimize Electrical System Damage and OutagesLightning/Transient Suppression EquipmentEqualize potential differences across the station grid & in the control buildingSystems redundancy emphasized on Bulk Power and system-significant generation

    Grounding and Bonding Basics40Years of Service19692009

  • Telecommunications GoalsSafetyBonding of metallic componentsReliabilityLightning protection and mitigation outdoorSingle Point Ground Location for all attachments (Main Ground Bus)Minimize equipment damageMinimize telecom circuit outage timeEquipment and systems redundancy emphasized on BroadbandReduce electrical noiseReference for DC voltage

    Grounding and Bonding Basics40Years of Service19692009

  • Substation Grounding A Great Start!All outdoor metallic components are bonded to earth groundBreakersTransformersStructuresStatic Wires/OPGWDistribution NeutralsStation ServiceLightning Shielding (masts, overhead shield wires, etc.)

    Control House4/0 copper grounding conductors brought in from grid (multiple places typically) CAUTION!!!4/0 conductors snaked through cable trench/cable tray system, reduced to AWG #6 as needed for rack/panel connectionRelay/Metering/Control Panels tied to bond snake running through the trench or tray cable management system40Years of Service19692009

  • ANSI/IEEE Substation Grounding Standards IEEE 80: Guide for Safety in AC Substation Grounding

    Technical Target: Outdoor AC substationsPurpose:Establish safe limits of potential differences human body interfaceSubstation grounding practices review for safety/safe design practicesProvide a procedure for the design of practical grounding systems based on the aboveDevelop analytical methods to aid in the understanding of gradient problems

    DOES NOT PROVIDE GUIDANCE FOR TELECOM RELIABILITY!!!40Years of Service19692009

  • Telecom Friendly Aspects of IEEE 80Core benefits of an IEEE 80 ground grid design for TelecommunicationsExcellent low net ground grid resistance, ohm is possible, depending on final designSite specific ground grid designHuman safe design, from a step-and-touch perspectiveGround Potential Rise voltage is typically limited and affected by step-and-touch design criteria

    40Years of Service19692009

  • Safety minimize potential differences between metallic pathsReliability ensure proper comm circuit operation despite transient conditionsEliminate ground loopsEstablish single point ground reference point in any one defined area (such as a control building room)Provide an engineered design for grounding and bonding in an area with telecom equipmentGrounding and Bonding Goals For Telecom40Years of Service19692009

  • Fundamental Differences Between Substation & Telecom Grounding (Control House)SUBSTATIONNot engineered by site, considered a standard practice.Grounding conductors can enter the control house in multiple locations and are tied to the station ground grid at different pointsRacks bolted directly to the floor and to each otherFloating DCFloor materials varyNo minimum ground/bond conductor radius typically specified TELECOM SITEEngineered on a site basis (can be templatized)Single point connection to ground fieldRacks are isolated from the floor and from each otherDC (+) is groundedFloor materials are conductive/anti-staticMinimum Bend Radius Specified for transient flow40Years of Service19692009

  • Telecom Grounding & BondingDefinitionsGrounding providing an engineered, low impedance path to earthBonding the permanent joining of metallic parts to form an electrically conductive path which will assure electrical continuity and the capacity to safely conduct any current likely to be imposed, including 60Hz and transientsGrounded Conductor a system or circuit conductor that is intentionally grounded (these normally carry current)Example: Electrical neutral wire, the DC (+) cable in 48 V DC Telecom suppliesGrounding Conductor a conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode or electrodes (these do not normally carry current)Example: AC Circuit electrical ground wire (the green wire), grounding wires used to interconnect racks, equipment bonding jumpers40Years of Service19692009

  • Telecom Grounding & BondingDefinitions (contd)Solid Ground an intentional connection to a grounding system, using a grounding wire in which there is no additional impedance imposedIncidental Ground an unplanned grounding connection. Example a conductive cabinet attached to a concrete surface via Tapcon screws can be said to be Incidentally GroundedEarthing Electrode a copper or copper-clad steel rod driven into the earth to provide a lower impedance path to true earth ground. Other types of earthing electrodes are steel

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