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
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INTERCONNECTIONS
Three major electric system networks; Reliability Councils
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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.
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MISO
 Kewaunee
 Point Beach
 Fermi
 Davis-Besse
 Perry
 Duane Arnold
PJM
 Braidwood
 Byron
 Dresden
 LaSalle
 Quad Cities
 DC Cook
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AmerenIP
 Clinton
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Michigan Electric TC
 Palisades
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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
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GL required information on communications between plants
and ISOs/TSOs
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GL also required information regarding Energy Management
Systems (analytical tools to monitor grid operations)
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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 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
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Power Factor and Reactive Power
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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.
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Reactive Power = Voltage Support
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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
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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.
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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.
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No longer able to provide customers’ expected energy requirements.
Forsee need to implement procedures including, but not limited, to:
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Public appeals to reduce demand.
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Voltage reduction.
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Interruption of non-firm end use loads in accordance with applicable
contracts.
During Alert 2, affected entities have the following responsibilities:
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Notifying other Balancing Authorities and market participants.
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Declaration period.
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Sharing information on resource availability.
ALERT 3 — Firm load interruption imminent or in progress.
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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
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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
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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.
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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
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