Grid Operations

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Grid Operations
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Purpose Basic Understanding of Grid
Operations/Blackout/Recovery

• Electric Power Grid Structure
• Reliability Councils/ISOs/TSO/RTOs
• GL 2006-02 Information
• Causes of Blackouts
• Blackout Recovery Procedures
• NERC Emergency Declarations

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INTERCONNECTIONSThree major electric system
networks Reliability Councils
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Independent System OperatorsTransmission System
Operators
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Independent System Operators (ISO)Transmission
System Operators (TSO)

• ISO/TSOs rely upon real-time data about the
  electric system to buy and sell power, and
  arrange transmission service.

• MISO
• Kewaunee
• Point Beach
• Fermi
• Davis-Besse
• Perry
• Duane Arnold
• PJM
• Braidwood
• Byron
• Dresden
• LaSalle
• Quad Cities
• DC Cook

• AmerenIP
• Clinton
• Michigan Electric TC
• Palisades
• NSP System Control Center
• Monticello
• Prairie Island

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GL 2006-02 Grid Reliability and the Impact on
Plant Risk and the Operability of Offsite Power

• GL required information on communications between
  plants and ISOs/TSOs
• GL also required information regarding Energy
  Management Systems (analytical tools to monitor
  grid operations)
• State Estimator provides a real time ac power
  flow model and system snap-shot using known V,
  and Amps for sections of grid and calculating V,
  Amps, MW, MVARs in other areas and then compares
  against telemetered data (every 2 min)
• Real Time Contingency Analysis what if study
  to determine what problems might result as lines
  and transformers are taken out of service (every
  5-10 minutes)
• First contingency analysis or N-1 refers to
  an analysis performed assuming the unexpected
  failure or outage of a single component, such as
  a generator, a transmission line, or a
  transformer (e.g. trip of NPP or largest
  generator)

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State Estimator
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Major Causes of Blackouts

• Voltage Collapse results from local reactive
  power deficiency
• Cascading Thermal Overloads thermal
  transmission overloads due to lines sagging into
  vegetation.
• Dynamic Instability results from systems
  inability to dampen normal oscillations after a
  disturbance. Generators swing against each
  other resulting in large MW and MVAR swings.

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Reactive Power

• Reactive power is a concept to describe the loss
  of power in a system arising from the production
  of electric and magnetic fields
• In power transmission and distribution,
  significant effort is made to control the
  reactive power flow. This is typically done
  automatically by switching inductors or capacitor
  banks in and out, by adjusting generator
  excitation, and by other means.
• A voltage collapse occurs when the system is
  trying to serve more load than the voltage can
  support

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Power Factor and Reactive Power

• Power Factor Active power/Apparent power
  kW/kVA
• Active power/ (Active Power Reactive Power)
• kW/(kWkVAr)
• Beer/(Beer Foam)
• The more foam (higher kVAr) indicates low power
  factor and vice versa.

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Reactive Power Voltage Support

• Transmission system voltage is needed to transfer
  power from generation stations to the load
  centers
• Reactive power (VARs) is the component of total
  power that maintains voltages across the system
• Sufficient voltage is maintained by supplying the
  transmission system with reactive power from
  generating stations and static devices
  (capacitors)
• Customer loads consume reactive power, as do
  heavily loaded transmission lines
• Reactive power cannot travel long distances
  because it meets considerable resistance over the
  transmission lines.
• As transmission lines become more heavily loaded,
  they consume more of the reactive power needed to
  maintain proper transmission voltage
• When reactive supply is limited, the increased
  loading will cause a voltage drop along the line.
  
• If reactive supply is not provided at the end of
  the line, the voltage begins to rapidly drop.
• If the transmission system can no longer transfer
  power from distant generation to energy users
  system begins to separate.

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Voltage Collapse (V-Q curve)
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Blackout Recovery Procedures

• Establish Generation
• Blackstart units can start and synchronize to the
  system without system ac power (compressed air
  start, battery powered electric motor, etc )
• hydros can be started quickly
• small Combustion Turbines-jet technology (10
  minutes)
• large CTs (up to an hour)
• steam units (e.g., coal) (1-20 hours)
• Priorities pre-established
• nuclear plant auxiliary power
• generating unit auxiliary power
• substation power
• natural gas or oil supply facilities

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Blackout Recovery Procedures

• Island isolated area where generation and
  load is essentially balanced
• Approach to system restoration is pre-planned.
  Options
• Single island black start unit, identify
  transmission paths/loads, expand island
• Multiple island black start units, pre-selected
  loads, separate restoration process, islands
  synchronize
• Core island one or a few large core islands
  used with multiple control centers involved
• Backbone island large island, ties in smaller
  areas and avoids synchronizing large islands

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NERC Emergency Declarations

• NERC has established three levels of Energy
  Emergency Alerts
• Reliability Coordinators will use these terms
  when explaining energy emergencies to each other
• An Energy Emergency Alert is an emergency
  procedure, not a daily operating practice

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NERC ALERT DEFINITIONS

• ALERT 1 All available resources in use.
• All available resources are committed to meet
  firm load, firm transactions, and reserve
  commitments concern about sustaining Required
  Operating Reserves
• ALERT 2 Load management procedures in effect.
• No longer able to provide customers expected
  energy requirements.
• Forsee need to implement procedures including,
  but not limited, to
• Public appeals to reduce demand.
• Voltage reduction.
• Interruption of non-firm end use loads in
  accordance with applicable contracts.
• During Alert 2, affected entities have the
  following responsibilities
• Notifying other Balancing Authorities and market
  participants.
• Declaration period.
• Sharing information on resource availability.
• ALERT 3 Firm load interruption imminent or in
  progress.
• Foresee or implementing firm load obligation
  interruption.
• Continue actions from Alert 2. The emergency is
  posted on the NERC website.

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DEFINITIONS

• Black Start Unit. A generating unit with the
  ability to go from a shutdown condition to an
  operating condition and start delivering power
  without assistance from the transmission system.
• Blackout (System Shutdown). The disconnection of
  the source of electricity from all electrical
  loads in a certain geographical area brought on
  by insufficient generation, an emergency-forced
  outage, or other fault in the generation/transmiss
  ion, distribution system serving the area.
• Combustion Turbine. A generating unit in which a
  combustion turbine engine is the prime mover for
  an electrical generator. It is typically used for
  peak shaving operation due to quick response
  capability.
• Emergency Maximum Generation Limit. The most
  amount of generation which can be produced by a
  unit and still maintain it at a stable level of
  operation.

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DEFINITIONS - contd

• Operating Reserve. Reserve capability which can
  be converted fully into energy within 30 minutes
  from the request of the PJM System Operator.
• Reactive Power. The product of voltage and the
  out-of-phase component of alternating current.
  Reactive power, usually measured in MVAR, is
  produced by capacitors and overexcited generators
  and absorbed by reactors and other inductive
  devices.
• Reserves.
• Operating Reserve - Generation available in 30
  minutes
• Spinning Reserve - Synchronized generation
  available in 10 minutes.
• Quick-Start Reserve Non-sychronized reserve
  available in 10 minutes.
• Secondary Reserve Reserve available in 11- 30
  minutes
• Synchronous Condenser. A synchronous machine
  which operates without mechanical load to supply
  or absorb reactive power for voltage control
  purposes.

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NRR Daily Grid Status Reporthttp//nrr10.nrc.gov/
DEVELOPMENT/GRIDSTATUS/gridstatus_current.ppt
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Important Points

• State Estimator
• Real Time Contingency Analysis
• First contingency analysis
• ISOs/TSOs
• Causes of Blackouts
• Voltage Collapse (lack of reactive power)
• Thermal Overloads (lines or vegetation growth)
• Dynamic Instability (generation/load imbalance)
• NERC Emergency Declarations