Transcript Electricity Restructuring - Enhancing Reliability of the North

Enhancing Reliability
of the North American Transmission Grid
April 5, 2001
NGA Forum
On Electricity
Restructuring
Presented By
Dejan J Sobajic
Power Delivery
EPRI
(650) 855-8537
[email protected]
Grid Reliability and Its Components
Grid
Operations
Load
Management
Integrated
Resource
Planning
Financial
Incentives
System
Maintenance
Obligation to Serve
Financial
Risk
Management
Information
Security
Operations
Planning
Power
Markets
Reliability
Management
Grid Reliability and Its Components
Grid
Operations
Load
Management
Integrated
Resource
Planning
Financial
Incentives
System
Maintenance
Incentive to Serve
Financial
Risk
Management
Information
Security
Operations
Planning
Power
Markets
Reliability
Management
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 reliability
analysis with economic
decision making.
Risk Definition
• Risk[impact i] = Prob[impact i] x Cost[impact i]
• This is an expectation of the economic impact of impact i
• It is the average cost associated with impact i over a long
period of time.
• We also compute the variance from this average.
• Risk of several impacts can be summed to get a composite
risk for an operating condition
• Risk of a trajectory of operating conditions can be summed
to get a cumulative, composite risk for a time interval.
Line Flow
Risk Based
Security Contours
SECURE
Interface Flow
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
The Risk-Based Decision Criteria
Max{benefit-risk}
10E+9
10E+7
10E+5
10E+3
10E-1
10E-3
10E-5
MW Flow on Transmission Interface
EPRI Reliability Initiative
• Started in Fall 1999
• Phase 1 closing on April 20, 2001
• “Proof-of-Concept” Studies
–
–
–
–
Risk Security Study of Southern Control Area of SERC
Risk Security Study of AEP System
Risk Security Study of Eastern Interconnection
Risk Security Study of ERCOT
• Phase 2 will be launched on April 20, 2001
• Key developments for future use of risk-based security
technology:
– Culture Change
– Data
Dejan (Dan) J. Sobajic - EPRI
• Phone : 650 – 855 - 8537
• Cell : 650 – 799 – 7670
• Email: [email protected]