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Substation DesignGeneral Concepts / Electric Equipment
Colegio de Ingenieros y Agrimensores de Puerto RicoAngel T. Rodríguez Barroso and Doeg Rodríguez
August 26, 2010San Juan, P.R.
Objective
The objective of this seminar is to provide a basic guide to select the electrical equipment and other systems in order to design a substation
Substation
An assembly of equipment in an electric system through which electrical energy is passed for generation, transmission, distribution, interconnection, transformation, conversion or switching.
General ConceptsElectrical Equipment
Based on the type of equipment a Substation could be :
Outdoor type with air insulated equipmentIndoor type with air insulated equipment
Outdoor type with gas insulated equipmentIndoor type with gas insulated equipment
Mixed Technology
Outdoor type with air insulated equipment
Outdoor type with gas insulated equipment
Indoor type with gas insulated equipment
Indoor type with gas insulated equipment
Mixed
Substation ProjectConcepts
Process starts with a need1. System deficiency is identified
Equipment upgradeLoad, Short Circuit , New Technology, High Voltage
Load increaseNew Equipment
Service reliabilityGenerators, SVC, Energy Storage
Service qualityExpansion or generation addition New regulations
Substation ProjectConcepts
1.a. System Deficiency StudiesLoad FlowShort Circuit, Arc-flash & Breaker DutyGroundingInsulation CoordinationProtectionCable AmpacityPower Factor Correction ( ATP )
Substation ProjectConcepts
2. Devise a project planDevelop project scope & estimate
Description including references to other elementsSingle-line diagram (s)Estimates System and operational restrictions Time constraints
Substation ProjectConcepts
3. Formal plans and drawingsRecordsDrawings
Site information as permits, surveys, geological surveys, equipment specifications, restrictions, and legal contractsConstruction drawingsSupplier lists
Material lists and specifications
Single Line
Diagram
Single Line DiagramSingle Line Diagram
Diseño Sub-w\Single line-1a.pdfE-1 One line diagram Model (1).pdf
Preliminary DesignPreliminary Information
New or existing siteIf existing, last drawings, as-built, data collection
Design guides or standardsDescription of propertyPrevious studiesExpansion plan
SubstationBasic
Equipment
Equipment and Systems
BreakersTransformersLine & breaker switchesSurge arrestersPotential transformersCurrent transformersSubstation Bus
CapacitorsProtection & ControlMeteringCommunicationsAuxiliary systemsGrounding & Masts
Bus Arrangements
SUB-des-bus034.pdf
Bus Arrangements
Cost of configuration Cost SpaceSingle bus $1.00 P.U. 1.0Single bus with tie breaker $1.22 P.U. 1.2Main & transfer bus $1.38 P.U. 1.7Ring bus $1.15 P.U. 1.2Breaker & a half $1.63 P.U. 2.0Double bus Double breaker $2.06 P.U. 3.0
Bus CharacteristicsInsulators
Voltage Class 46 kVMaximum System Voltage 48.3 kV60 cycle wet flash over (kV) 100Impulse withstand (kV) BIL 250Leakage distance (in.) 43Dry arcing distance (in.) 17Tensile strength (lb.) 14,000Cantilever strength (lb.) 2,000
Bus CopperAluminum
StructureGalvanized structure in compliance with hurricane and seismic criteria
Equipment Insulation Surge Arresters
Functions:Limit transient surge voltages below the insulation breakdown of the equipment
Provide transient voltage protection while connected to the power operating voltage
Surge Arrester SelectionAll arresters use Zinc Oxide valves (MOV)For selecting you will need:
Power operating voltage ratingEnergy dissipation capabilityType or arrester classDo an insulation coordination study
Arrester SelectionTOV- temporary overvoltage are
cause by:Line to ground faultsNeutral lossSwitching surges
To select check:1. MCOV -Maximum Continuous
Over Voltage For grounded system
MCOV> 1.05VLG or MCOV> TOV
Ungrounded worst case is MCOV>VLL
2. Arrester Energy DissipationManufacturer provides the information but it requires a Transient Study to establish the rating
3. Type Station or intermediate
protection level, energy capability, mechanical strength, pressure relief rating
Arrester Selection4. Arrester protective characteristics
Impulse voltage levelBIL-- Basic Impulse LevelBSL– Basic Switching Surge Level
( Wave form 83% of BIL crest voltage)
Limit the lead length to a minimum
Surge ArresterPhotos
Surge-1.pdfArrester-works-3-4.pdf
Lightning Protection
Empirical Design Methods1. Fixed Angles2. Empirical Curves
Electrogeometric ModelStandard IEEE 998-1996
Shielding WiresBig substations
MastsSmall substations
They are composed of three elements:
1. Air terminals at appropriate points2. Down conductors to carry current to ground3. Grounding electrode to carry current into the earth
Lightning ProtectionMethods
MASTMETHOD.pdf
TransformersLosses
No load lossesHysteresisEddy currents
Load lossesLeakage flux & magnetic fluxRegulation
Load Tap ChangerNo load Tap Changer
TypesMultiwindingAuto transformers
lower costsmaller sizelower regulationlower losseslower impedanceno delta connection
TransformersRating
Self cooled ONAN oil natural, air natural circulation
Forced Air Rating ONAF oil natural, air forced circulation
Forced Oil Rating OFAF oil forced, air forced circulation
RatingTransformers 2.5-10 MVA
One 125% stage coolingTransformers >10 MVA
Two cooling stages 133% ONAN166% ONAN
Continuous loading with oil hot spot less than 110 degree C
Short term loading 180 degree C
TransformersCheck Rating of:
Current transformersBushingsWindingsConnectionsLoad tap changers
FailuresShort circuits
Bushing contaminationLoad tap changer
Contaminated oilContact erosionCompartment short circuits
TransformersOil Preservation
Sealed tankInert Gas
Nitrogen blanket over oilModified Conservator
Main tank is filled of oil from a conservator tank
Winding connectionsDelta-Wye
NLT, LTC location?Wye –Delta
NLT, LTC location?Delta –Delta
NLT, LTC location?Three winding transformers
NLT, LTC-location
Transformer Fire ProtectionTransformer-Prot.-2A.pdf
ElectricalTransformer Differential Protection & Fast Breaker
MechanicalBarriersDeluge-SprinklersTransformer-Prot.-1.pdfCompress-Air-FoamPressure/MechanicalProtector016.pdf
Instrument Transformers
Potential TransformersType
Insulating mediumOil -porcelainDry – composite
Medium to low voltageRated by
Rated voltage & ratio H/S BILThermal rating
Current Transformers
Type Insulating medium
Oil -porcelainDry – composite
Medium to low voltageRated by
Rated voltage & ratio H/S BILClass relay or metering
Instrument Transformers
Potential TransformersANSI/IEEE C57.13Inductive & capacitor (CVT) type
ANSI accuracy of 0.15%, 0.3%, 0.6%, 1.2%
at burdens W, X, Y, Z and ZZ (400VA at PF=.85).
Optical voltage transducer
Current TransformersANSI/IEEE C57.13Relay ClassMR 10 C200, MR 10 C400Class C is for low leakage (donut)Class T is for high leakage (bar-type)
Metering Class0.15%, 0.3%, 0.6%, Accuracy at burdensB0.1, B0.2, B0.5, B1.0 and B1.8
Optical Current transducer
Instrument Transformers CT-PT-DIS.pdf
BreakersDefinition:
Is an automatically operated electromechanical device designed to protect an electrical circuit from damage caused by a short circuit or an overload
Breakers Type
ClassificationsInterrupting medium
Air blastingOil (high & low volume)Vacuum (medium voltage)Gas SF6 (high voltage)Magnetic Air (distribution)
TankDead tankLive tank
Three Phase Closing &Single Phase Closing
Ratings – ANSI C37.06Rated voltageInsulation levelContinuous currentInterrupting current at rated
voltageTransient recovery voltageRated interrupting timePermissible trip delay
Breakers
Scan-Sub-Des\SUB-des-BR1024.pdfScan-Sub-Des\SUB-des-BR2025.pdf
Distribution-breaker.pdf
Capacitors
Benefits
Provides reactive power Power factor correction
Voltage regulationLoss reduction
Improve system capacity
Studies
Load flowShort circuit
Transient analysisHarmonics
Protection schemeMeasurements
Capacitor StudiesLoad Flow
Needs, bank capacity, location, losses, voltage regulation
Transient StudyConnection grounded or ungrounded, Overvoltage, overcurrent, insulation coordination, surge arresters.Limit overvoltage to less than 10 % of rated voltage
Short CircuitProtection, unbalance scheme
HarmonicsFilter design
Capacitors
SUB-de-cap035.pdfSUB-de-cap-stu036.pdf
SUB-de-cap-PROT037.pdf
Capacitors
EN-LV03-09_2006-wall_mounted_automatic_cap_bank.pdf
SwitchesTypes
StationTransmissionDistributionLow voltage
SwitchesType & Purpose
Single phase andGang operated three
phaseProvide isolation of:
equipment linesbuses
Allows for maintenance & testing Interruption for small currents
RatingsSpecified ANSI C37.32 & IEEE
C37.34Rated continuous currentRated maximum voltageRated short circuit-time current
(momentary)Rated mechanical operationsRated interruption capabilityRated ice breakingRated Insulation level
SwitchesMounting arrangements
Horizontal uprightSingle sideDouble sideCenter side Double side V
VerticalUnderhung or inverted
Underground
Grounding SwitchFor grounding live parts at the stationFor grounding linesSingle pole or gang operated
Switches
Switches
SwitchesTrayer.pdf
Scan-Sub-Des\SUB-DES-SW-tables.pdf
Station Power, Batteries ChargersAC Power
Two sources, emergency generator with transfer switch
Transformer cooling systemTransformer load tap changer Transformer cabinet heatersCircuit breakers stored energy
mechanismCircuit breakers cabinet heatersBuilding & Outdoor yard lightsBattery chargers & outletsBuilding mechanical systemBuilding A/C
DC ServiceTwo battery banks
Two DC distribution panelOne circuit per breaker from
each panel ( combine)For relay panel, one circuit
from each panelTwo circuit per transformer
Use IEEE Std 485 for sizing lead acid batteries
BatteriesType of batteries
VentedLead-calcium flooded cellLead-selenium flooded cellNickel-Cadmium flooded
cellValve Regulated Sealed
Design PracticesDesign a room exclusively for
batteriesDesign a room for two batteriesDesign battery room with a system to
minimize hydrogen build upProvides acid spills containmentProvide plastic shields over energize
partsProvides safety equipment Consider hydrogen sensorsConsider microprocessor controlled
chargers
CablesHigh voltage cables
Client/PREPA regulations & buy cables from approved manufacturers
Shielded cable TR-Cross-linked PolyethyleneEPR Ethylene Propylene Rubber
Low voltage Cables (600V)
Copper cable is more reliableMulticonductor, color coded cable
is preferred Practice is:PT circuits #12 AWG CUCT circuits #10 or # 8 AWG CUControl Circuits # 14 AWG CUSCADA alarms #18 AWG CU
Substation Automation & Control
Deployment of substation and feeder operating functions and applications to enhance operations and maintenance
efficiencies with minimal human intervention.
SA ArchitectureBasic Layer Architecture
Process Level ( HV Equipment)Bay Level (Protection & Control)Station level
HMI Architecture-1.pdf
Communication ProtocolsIEC 61850
Communication Networks & Systems in Substation
ScadaReal-timeSelf description
Information modelsConfiguration language
IEC-61850-AP.pdf
Distributed Network Protocol DNP3
Communication Protocol IED devices
SCADAalc-2012.pdf
Protection
Relays are devices that are connected throughout the electric power system to detect an undesirable conditions and start an action to minimize damages to the system
Protection
Protection philosophy requires a balance between redundancy and cost
The goal is to protect the system with the simplest design
The more complex the protection scheme the more probability for bad operations
ProtectionZones of protection
GeneratorsTransformersBusesTransmission LinesDistribution Lines
Zones of protectionPrimarySecondaryBack-up
Transformer ProtectionDifferentialOvercurrentOverexcitationSudden pressureGas detection
Bus ProtectionDifferentialOvercurrentBreaker failure
Protection
Line ProtectionNon-directional overcurrentDirectional overcurrentImpedancePower line carrier & pilot wireDistance & directional overcurrentCurrent differential (fiber optic channel) Phase comparison
Grounding StudyGrounding Grid General.pdfCombine-grounding-2.pdf
Line
Feed
Underground Feed
Underground FeedMuseoCar\9569-combine-car.pdf
Control &Protection
Panel
Control & Protection Panel
Visit to the SiteObserve all site advantages and constraints
Site restrictions (urban regulations)Check for future expansion constraintsHow lines and load circuits will be brought to the site and exit outAccess to the site (how to move heavy equipment)
Equipment LayoutGeneral System Layout
Diseño Sub-w\VIEQ Subst Profile 1.pdfGIS-PDF\GIS-Estudio\GIS-layout017.pdf
Post Visit to SiteUpdate project scope & get approval if
requiredUpdate estimate if required
Submit amended permits if requiredAdjust any design criteria if required
Issue instructions for long lead equipment and site studies
Equipment Lead Time
Substation Transformers 10 -16 monthsCircuit Breakers 4 – 8 monthsHigh Voltage Switches 4 – 8 monthsControl & Protection Panel 4 – 8 monthsHigh Voltage GIS Equipment 8 – 12 months Medium Voltage GIS 8 – 10 months
Developed Project Time TableExpected Service DatePermitsEquipment Procurement (transformers, breakers, etc. lead time)Power supplier requirements (PREPA and others)Client operations inputGet the approval:
SLD drawing Site Layout Detailed design ConstructionCommissioning and as-built
Substation LayoutSubstation LayoutSingle Line Diagram
Check:Numbers of breakers, disconnect switches, transformers,
auxiliaries, protective devices, lines and other equipment.Short circuit and current capacity of equipment, bus and other
equipmentCompliance with project’s scope and requirements Number of lines and load circuitsAll equipment fit within substation lot and complies with
standards
Substation LayoutFinalize design requirements
OutdoorHigh, low profile or GIS mixed
IndoorGIS or GIS mixed
System protection and power company requirementsOverhead lines & load circuits; clearancesUnderground lines & load circuits
Cables, Gas Insulated Lines, Bus (GIL, GIB)
Substation LayoutGeneral Layout
GIS-PDF\General-Layout-GIS.pdf
Questions?
Thank You
Substation DesignGeneral Concepts / Electric Equipment
Doeg RodríguezATRB, Ingenieros, CSP
787-236-6900Angel T. Rodríguez Barroso
MEC Engineering605 Condado Avenue
San Juan, P.R.787-977-5045,
TransformersSome of the Standards
IEEE STD C57.12.2000 ANSI STD C57.12.10-1997 IEEE STD C57.12.90-1999IEEE STD C57.12.01-2000IEEE STD C57.98-1993IEEE STD C57.91-1995IEEE PC 57.119 (Draft 14.0) 2001
ReferencesANSI C37 series – Protection and Control Equipment
ANSI C57 Series – TransformersIEEE Standard 80- Substation Grounding
NEMA Standards – Electric Equipment ConstructionNational Electrical Safety Code
Electric Power Substations Engineering 2nd EditionPREPA – Manuals and Standards
Electric Power distribution Engineering 2nd EditionRUS Bulletin 1724E-300
IEEE/ANSI Standards
