Enhancing Reliability Enhancing Reliability of the North American Transmission Gridof the North American Transmission GridEnhancing Reliability Enhancing Reliability of the North American Transmission Gridof the North American Transmission Grid
Presented By
Dejan J SobajicPower DeliveryEPRI(650) [email protected]
April 5, 2001
NGA ForumOn ElectricityRestructuring
Grid Reliability and Its Components
FinancialRisk
Management
GridOperations
PowerMarkets
ReliabilityManagement
OperationsPlanning
IntegratedResourcePlanning
SystemMaintenance
InformationSecurity
FinancialIncentives
Obligation to Serve
LoadManagement
Grid Reliability and Its Components
FinancialRisk
Management
GridOperations
PowerMarkets
ReliabilityManagement
OperationsPlanning
IntegratedResourcePlanning
SystemMaintenance
InformationSecurity
FinancialIncentives
Incentive to Serve
LoadManagement
Change of the Players
• Planning and operating bulk interconnected electric power systems was once mainly the domain of planning and operations engineers within the utility company.
• Now this involves entities representing the interests and needs of – transmission owners, – system operators, – energy sellers, – large industrial customers and other end users, – regulators, – reliability councils, – security centers, – manufacturers, – marketers, – brokers, and – power exchange personnel.
Change in System Operations
• In parallel with the increase in the diversity of participants, the conditions under which power systems are operated have also become more diverse.
• Transmission loading patterns differ from those for which they were originally planned.
Maintaining System Reliability is a Must
• Maintaining reliability is fundamental to the proper planning and operation of the bulk electric power system.
• Significant deterioration in reliability levels could have social and economic consequences that directly counter benefits of decreased energy costs brought about by competition.
Safety Margins
• To maintain system reliability under uncertainty, studies are performed to aid in operating and planning decisions.
• The current practice within the industry uses deterministic methods to perform these studies, with significant safety margins to cover "all" the possible unknown uncertainties.
• Though investment and operational costs are relatively high, this has resulted in a correspondingly high degree of reliability in most power systems.
Present Realities
• Economic pressures are pushing systems towards lower security margins.
• To operate the system closer to the traditional deterministic limits, or even beyond them, – more refined methods for power system
security assessment are needed at the operating and planning stage,
– which take into account the probabilistic nature of many uncertain variables in the decision-making environment.
Why Change?
• There has been a real and tangible price to pay for using this approach: solutions tend to be overly conservative, due to the emphasis of the most severe, credible event.
• Utilities are less willing to invest in new facilities yet more willing to push transmission limits in order to take advantage of less expensive energy and lower production costs.
Adequacy and Security
North American Reliability Council (NERC) Planning Standards defines:
• Adequacy is the ability of the electric systems to supply the aggregate electrical demand and energy requirements of their customers at all times, taking into account scheduled and reasonably expected unscheduled outage of system elements.
• Security is the ability of the electric systems to withstand sudden disturbances such as electric short circuits or unanticipated loss of system elements.
Three Causes of Insecurity
• We use the label "security," as the ability of the system to withstand sudden disturbances in terms: – circuit overload– voltage problems, and– dynamic problems.
• We are motivated to include these three types of problems under the same umbrella because our intent is to develop a single assessment framework to encompass all of them
Security Mapping
Risk and Reliability
Reliability is a measure of: a system’s ability to avoid failure.
Risk is a measure of: a system’s exposure to the consequences of failure.
Reliability analysis primarily aims to identify likely failure modes.
Risk analysis primarily aims to integrate reliabilityanalysis with economic decision making.
Risk Definition
• Risk[impact i] = Prob[impact i] x Cost[impact i]Risk[impact i] = Prob[impact i] x Cost[impact i]
• This is an This is an expectation expectation of the economic impact of impact iof the economic impact of impact i• It is the It is the average costaverage cost associated with impact i over a long associated with impact i over a long period of time.period of time.• We also compute the We also compute the variance variance from this average.from this average.• Risk of several impacts can be summed to get a Risk of several impacts can be summed to get a compositecomposite risk for an operating conditionrisk for an operating condition• Risk of a trajectory of operating conditions can be summedRisk of a trajectory of operating conditions can be summed to get a to get a cumulativecumulative, composite risk for a time interval., composite risk for a time interval.
Interface Flow
Lin
e F
low
Thermal
Dynam
ic
Voltage
SECURE
Risk BasedSecurity Contours
In an Operator Own Words...
• Operators need to know the probability of occurrence, and then determine whether or not to apply preventive actions…
• If certain transaction is going to increase the loading on certain facilities will it have have a significant effect on the security of the system?
• What is the value of taking that next step? and then "What is the cost of having a major disturbance occur?”
Composite Risk Contours Composite Risk Contours
The Risk-Based Decision Criteria
MW Flow on Transmission InterfaceMW Flow on Transmission Interface10E-510E-5
10E-310E-3
10E-110E-1
10E+310E+3
10E+510E+5
10E+710E+7
10E+910E+9
risk
risk
benefitbenefit
Max{benefit-risk}Max{benefit-risk}
EPRI Reliability Initiative
• Started in Fall 1999Started in Fall 1999• Phase 1 closing on April 20, 2001Phase 1 closing on April 20, 2001• ““Proof-of-Concept” StudiesProof-of-Concept” Studies
– Risk Security Study of Southern Control Area of SERCRisk Security Study of Southern Control Area of SERC– Risk Security Study of AEP SystemRisk Security Study of AEP System– Risk Security Study of Eastern InterconnectionRisk Security Study of Eastern Interconnection– Risk Security Study of ERCOTRisk Security Study of ERCOT
• Phase 2 will be launched on April 20, 2001Phase 2 will be launched on April 20, 2001• Key developments for future use of risk-based security Key developments for future use of risk-based security
technology:technology:– Culture ChangeCulture Change– DataData
Dejan (Dan) J. Sobajic - EPRI
• Phone : 650 – 855 - 8537Phone : 650 – 855 - 8537
• Cell : 650 – 799 – 7670Cell : 650 – 799 – 7670
• Email: [email protected]: [email protected]