PRESENTATION TO IEEE PES, ORLANDO CHAPTER:
“GROUNDING & BONDING CONSIDERATIONS FOR SUBSTATION COMMUNICATIONS AND “SMART GRID””
Developed and Presented By:Adrian G Zvarych, PEPrincipal EngineerTRC EngineeringMember, IEEE24 September [email protected]
Additional Contributions & Peer Review By: Michael Cunningham, Senior Engineer - TRC
Class Objectives
1. Understand Substation Grounding/Bonding Design Goals to Satisfy Communications Requirements
2. Review of Typical Substation Control House Grounding/Bonding Practices
3. Review Typical Telecom Room Grounding/Bonding Practices
4. Necessary Grounding & Bonding Elements for a Smart Grid Friendly and Communications – Ready Substation Control House
5. Look-Ahead for other opportunities
6. Review
40Years of Service
19692009
Change Has Been Happening
40Years of Service
19692009
Part 1: Substation Communications Evolution
Communications migration path:– Analog to digital– Discrete to multiplexed– Local Information decision needs to remote and diverse needs– Lower Reliability to High Reliability (design and need)– Minimal regulation (self- on inter-industry regulation to increased scrutiny and
regulation by others)
40Years of Service
19692009
Pilot Wire Interface& Isolation Transformers
Circa 1900’s Distribution Breakers
1912 – Manufactured GE Oil Break Switch…
STILL IN SERVICE!!!!
Legacy Substation Communications Systems
PEOPLE/OPERATIONS Station Operators with all local indication Communications to Control Center via Power Line Carrier or Telephone Company Copper
Circuits (SCADA) Radio Dispatch for Crews
RELAY PROTECTION Power Line Carrier (first digital form of substation communications “ON-OFF”) Copper Based Pilot Wire All analog meters and electromechanical relays Needs driven by electric utility operations & reliability
40Years of Service
19692009
Advancements in Legacy Substation Relaying and Communications
Driven by build out of high voltage and EHV transmission grid– Need for high speed and reliable/secure relaying– Need for remote and central monitoring and control of station equipment– First discrete component “solid state” relaying deployed in substations in the 1970s
Single Side-Band Power Line Carrier – more channels, more functionality Analog Point-To-Point Microwave Optical Networks
40Years of Service
19692009
Development of “Non-Copper” Substation Communications Systems
Analog Microwave (circa 1960’s) Digital Microwave (circa 1980’s) Spread Spectrum – 900MHz (circa 1980’s) Fiber (circa 1990’s)
40Years of Service
19692009
Advancements of Components/Technology
Protective Relaying Electromechanical Relays – Solid State Relays Solid State Relays – Microprocessor Relays
Communications Copper Analog Microwave Digital Microwave 900MHz – Licensed & Spread Spectrum/Unlicensed Fiber Discrete Analog Digital Multiplexed IP
40Years of Service
19692009
TELECOMMUNICATIONS CIRCUIT HIERARCHY
DS0-1
DS0-2
DS0-3
DS0-4
DS0-24
.
.
.
DS1-1
DS1-2
DS1-4
DS1-3
DS1-28
.
.
.
OC1-1
OC1-2
OC1-3
OC3-1
OC3-2
OC3-3
OC3-4
OC12-1
OC12-2
OC12-3
OC12-4
OC48-1
OC48-2
OC48-3
OC48-4
OC192
IMUX
JMUX
JUNGLEMUX EXPANDABLETO OC48 BANDWIDTH
BROADBAND CARRIER CLASS NETWORKS
DWDM
11 2424 672672 2,0162,016 8,0648,064 32,25632,256 129,024129,024 oooo
Phone linesper circuit type
And Now… Smart Grid!
Effects of Smart Grid and Communications Technology
Higher density of low-signal voltage circuits (RS-232, RS-485) over copper in the control house
More fiber in the control house More non-substation hardened devices entering the control house IT-Telecom teams becoming more involved in substation control houses Organizational awareness of substation environment vs data center/telecom room
requirements
40Years of Service
19692009
Users of Substation Information
System Operators P&C Engineering Asset Management Customer Service Center Field Maintenance Personnel (line trucks, P&C, substation, etc.) Electric System Customers (indirectly) Personnel Managers Corporate Security (access management, surveillance) IT-Security Cyber-Security Teams Utility Interchange (Where Transmission Tammy draws the line…) Others…
40Years of Service
19692009
Substation Communications: Change Is Here
Traditional Telemetry Watts, Vars, Volts, Amps Status Open, Closed, Major, Minor Control Open, Close, Raise, Lower Voice SCADA – Analog/4 Wire AC Data
Present Day All of the above, plus Temperature Outdoor Ambient, Control House Transformer Telemetry Winding Temps, Dissolved Gas, Tap Position Battery Voltage IP Services
– Security Surveillance, Door Access Control– High Speed Remote Access for IEDs– Syncrophasors– Local Employee LAN Access– SCADA
40Years of Service
19692009
“Change Is Here”
Increased data flow (to 27 TB/day or higher in larger utility systems) from substations Not just SCADA Non-Traditional organizations using or managing substation systems and information Increased deployment of non-station hardened equipment, despite efforts by IEEE to
develop standards such as IEEE-1613
40Years of Service
19692009
PART 2: NAVIGATING THE TRANSITION
GOALS OF GROUNDING/BONDING – SUBSTATION AND TELECOM BASICS AND DEFINITIONS REAL WORLD CASE STUDY
Substation GoalsSafety
– Step and Touch– Ground Potential Rise
Reliability– Lightning Mast/Shielding– Minimize Electrical System Damage and Outages– Lightning/Transient Suppression Equipment– Equalize potential differences across the station grid & in the control
building– Systems redundancy emphasized on Bulk Power and system-significant
generation
Grounding and Bonding Basics
40Years of Service
19692009
Telecommunications GoalsSafety
– Bonding of metallic components
Reliability– Lightning protection and mitigation – outdoor– Single Point Ground Location for all attachments (Main Ground Bus)– Minimize equipment damage– Minimize telecom circuit outage time– Equipment and systems redundancy emphasized on Broadband– Reduce electrical noise– Reference for DC voltage
Grounding and Bonding Basics
40Years of Service
19692009
Substation Grounding – A Great Start!
All outdoor metallic components are bonded to earth ground– Breakers– Transformers– Structures– Static Wires/OPGW– Distribution Neutrals– Station Service– Lightning Shielding (masts, overhead shield wires, etc.)
Control House– 4/0 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 connection– Relay/Metering/Control Panels tied to bond ‘snake’ running through the trench or tray cable
management system
40Years of Service
19692009
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 interface Substation grounding practices review for safety/safe design practices Provide a procedure for the design of practical grounding systems based on
the above Develop analytical methods to aid in the understanding of gradient problems
DOES NOT PROVIDE GUIDANCE FOR TELECOM RELIABILITY!!!40Years of Service
19692009
Telecom – Friendly Aspects of IEEE 80
Core benefits of an IEEE 80 ground grid design for Telecommunications Excellent low net ground grid resistance, ½ ohm is possible, depending on final
design Site – specific ground grid design Human – safe design, from a step-and-touch perspective Ground Potential Rise voltage is typically limited and affected by step-and-touch
design criteria
40Years of Service
19692009
Safety – minimize potential differences between metallic paths Reliability – ensure proper comm circuit operation despite transient conditions Eliminate ground loops Establish 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 equipment
Grounding and Bonding Goals For Telecom
40Years of Service
19692009
Fundamental Differences Between Substation & Telecom Grounding (Control House)
SUBSTATION1. Not engineered by site,
considered a ‘standard’ practice.2. Grounding conductors can enter
the control house in multiple locations and are tied to the station ground grid at different points
3. Racks bolted directly to the floor and to each other
4. Floating DC5. Floor materials vary6. No minimum ground/bond
conductor radius typically specified
TELECOM SITE
1. Engineered on a site basis (can be templatized)
2. Single point connection to ground field
3. Racks are isolated from the floor and from each other
4. DC (+) is grounded
5. Floor materials are conductive/anti-static
6. Minimum Bend Radius Specified for transient flow40
Years of Service
19692009
Telecom Grounding & Bonding
Definitions “Grounding” – providing an engineered, low impedance path to earth “Bonding” – 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 transients
Grounded 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 supplies Grounding 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 jumpers40
Years of Service
19692009
Telecom Grounding & Bonding
Definitions (cont’d)
Solid Ground – an intentional connection to a grounding system, using a grounding wire in which there is no additional impedance imposed
Incidental Ground – an unplanned grounding connection. Example – a conductive cabinet attached to a concrete surface via Tapcon screws can be said to be ‘Incidentally Grounded’
Earthing 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 well casings, structural steel ground grids, metallic piping for water, sewer, etc.
True Earth Ground – a virtual location beneath the earth’s surface, where electrical resistance and impedance is zero, and ‘ground’ currents run freely, whether man-made or natural
Skin Depth – a frequency and materials dependent calculation which determines the penetration of current flow density into the surface of a conductor. http://www.microwaves101.com/encyclopedia/calsdepth.cfm
40Years of Service
19692009
Telecom Grounding & Bonding
Components of a Telecom Grounding & Bonding System at a SubstationCHPGP: Control House Principal Ground Point
A ground bus bar located near the cable connection to the substation ground grid. It serves as the central connection point for all main grounding conductors and earthing electrode
Horizontal EqualizerAn insulated grounding conductor which has it’s origination point at the CHPGP, with the
function of connecting conductive equipment in a home run fashion to the principal grounding point in the room
Halo GroundA grounding conductor, supported on insulated stand-offs around the perimeter of the room,
typically installed at seven feet or higher elevation, to which all peripheral equipment are bonded (HVAC, Heaters, Junction Boxes, etc.). The Halo is a radial connection, and not a complete electrical loop.
Mechanical and Exothermic ConnectionsCable-to-device or cable-cable connections. Outdoor connections are typically exothermic,
in-building connections are typically mechanical compression, with two-hole lugs.Hardware & Miscellaneous
Insulated stand offs, cable management, plexiglas or Lexan shields, stainless steel nuts & bolts, no-oxide grease, exothermic weld molds, mechanical connectors, etc.
40Years of Service
19692009
Case Study: Wind Farm Control House Application
Attributes: Collector Station (34kV-230kV) yard adjacent to transmission switching station Transmission switching station has microwave tower for Primary relaying channel,
SCADA, and internal voice communications Copper leased entrance cable, with isolation, at Transmission control house Transmission control house has “PRIMARY” and “SECONDARY” rooms Communications racks and telco isolation equipment in PRIMARY room PA System in place to cover the switchyard (copper connections to yard corners)
40Years of Service
19692009
Grounding-BondingCommunications Tower & Outside Facilities
Wireless communications for Smart Grid• Requires lightning protection @ top• Proper bonding along feedline route
• Bond @ antenna• Bond prior to horizontal transition• Bond prior to CH entry• Center conductor protection just inside CH
• Driven rods @ tower & feedline entrance
STATION GROUND GRID
40Years of Service
19692009
Case Study Substation
Overall Communications Elementary
Control House Floor Plan
40Years of Service
19692009
Ice Bridge Detail
40Years of Service
19692009
Inside Wall Elevation
40Years of Service
19692009
Cross Section Elevation
Control House Bonding Connections
Grounding-Bonding Inside The Control House
Key Design Features:• Single Point Ground Bus (no ground loops)• Discrete (insulated preferred) home-run bonding connections to all equipment
connections:• Cable tray & rack taps• AC System Neutral @ AC Panel• Telecom Reference Ground point• Substation ground grid connection• Building steel• Microwave feedlines
Departure From Telecom Practice• Racks directly bolted to floor and each other without isolation• Cable trays may not be bonded across joints• Grounding conductors not insulated40
Years of Service
19692009
A Few Images…
SCADA “Master” 900 MHz Transceiver 900 MHz SCADA “Remote” 900 MHz Transceiver – Indoor Mount
“Smart” Recloser “Master” Tower
Tower Leg Bonding
Halo Ground
Simple Feedline Entrance
Outdoor Main Ground Bus Mounting
Insulated Stand-Off
Feedline Entrance
Ground Bus Bar Example
1. Main Ground Bus…“Producers” and “Absorbers” SeparatedClear separation of power, grounding, and data cables
DC (+) Ground Reference…
“A” and “B”Battery Strings
SeparatelyGrounded
Isolation pads under rackAnti-Static floor tiles
Look-Ahead – Other Opportunities
Cable Management– Low Voltage Serial Connections: RS-232/485, GPS– Ethernet– Fiber Optic Entrance and Patch Cables
Non-Substation Hardened Equipment Security (card access, surveillance, etc.) Working with teams outside “Transmission Engineering”
Summary
Communications Grounding-Bonding practices require safety, but also reliability
Control House equipment connects to a single – point ground bus bar to which all metallic elements are bonded
Soft – radius bends for all grounding and bonding connections
Minimize or eliminate ground loops
THE ROAD TO THE FUTURE IS BRIGHT FOR POWER AND SMART GRID COMMUNICATIONS…
Are you ready?
