Grid Operations

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 2

INTERCONNECTIONS

Three major electric system networks; Reliability Councils 3

Independent System Operators Transmission 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     PJM  Fermi Davis-Besse Perry Duane Arnold      Braidwood Byron Dresden LaSalle Quad Cities DC Cook    AmerenIP  Clinton Michigan Electric TC  Palisades NSP System Control Center  Monticello  Prairie Island 5

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) 6

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 system’s 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 9

Power Factor and Reactive Power

   Power Factor = Active power/Apparent power = kW/kVA = Active power/ (Active Power +Reactive Power)  = kW/(kW+kVAr)  = Beer/(Beer +Foam) The more foam (higher kVAr) indicates low power factor and vice versa. 10

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 13

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 14

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/transmission, 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 - cont’d

   

Operating Reserve.

fully into energy within 30 minutes from the request of the PJM System Operator.

Reserve capability which can be converted

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 Report

http://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 20