System for optimizing power network design reliability

• US 5,798,939 A
• Filed: 10/14/1997
• Issued: 08/25/1998
• Est. Priority Date: 03/31/1995
• Status: Expired due to Term

• Current Assignee: ABB Incorporated (ABB Limited)
• Original Assignee: ABB Power T&D Limited (ABB Limited)
• Inventors: Hirt, Robert L., Ochoa, J. Rafael
• Primary Examiner(s): Trans, Vincent N.
• Application Number:
  US08/950,333
• Time in Patent Office: 315 Days
• Field of Search: 364/493, 364/492, 364/483, 364/578
• US Class Current: 700/286
• CPC Class Codes: G06Q 30/0283 Price estimation or determination
• CPC Class Codes: H02J 2203/20 Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
• CPC Class Codes: H02J 2310/60 Limiting power consumption in the network or in one section of the network, e.g. load shedding or peak shaving
• CPC Class Codes: H02J 3/00 Circuit arrangements for ac mains or ac distribution networks
• CPC Class Codes: H02J 3/144 Demand-response operation of the power transmission or distribution network
• CPC Class Codes: Y02B 70/3225 Demand response systems, e.g. load shedding, peak shaving
• CPC Class Codes: Y02E 40/70 Smart grids as climate change mitigation technology in the energy generation sector
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 10/50 Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
• CPC Class Codes: Y04S 20/222 Demand response systems, e.g. load shedding, peak shaving
• CPC Class Codes: Y04S 40/20 Information technology specific aspects, e.g. CAD, simulation, modelling, system security
• CPC Class Codes: Y04S 50/14 Marketing, i.e. market research and analysis, surveying, promotions, advertising, buyer profiling, customer management or rewards

Abstract

A computer workstation-based interactive tool for assessing the reliability of power systems is disclosed. This tool can be used to determine the effect on the reliability of both substations and bulk generation and transmission systems of system additions, design alternatives, maintenance practices, substation configurations, and spare part policies. Each utility using the present invention is modeled analytically. The model includes load characteristics, demand projections, voltage profiles, energy and operating constraints, operator and automatic responses to the occurrence of contingent events, generating unit dispatch, contingency remedial actions, load shedding practices, demand-side management, and equipment failure modes including planned and unplanned maintenance.

Claims

1. A computer-based interactive method for planning and operation of power systems, comprising the steps of:

(a) developing an analytical model of the power system; and

(b) determining the effect on reliability of the following;

system additions, design alternatives, maintenance practices, substation configurations, and spare parts policies;

wherein step (b) involves a consideration of economic cost of contingencies and economic value of service, said economic cost of contingencies including the cost of unavailability of electric power due to an outage of an element of the power system, and said value of service including the value to a customer of uninterrupted electric power; and

wherein contingencies are selected on the basis of a combination of a ranking of contingency severity and a probability of occurrence based on equipment statistics, said contingencies including transmission line overload, transformer overload, voltage above or below prespecified limits, busbar isolation, system islanding, and a reactive power requirement above an available level.

2. A computer-based interactive method for assessing the reliability of power systems, comprising the steps of:

(a) developing an analytical model of the power system; and

(b) determining the effect on reliability of at least one of the following;

system additions, design alternatives, maintenance practices, substation configurations, and spare parts policies;

wherein the model includes load characteristics, demand projections, voltage profiles, energy and operating constraints, operator and automatic responses to the occurrence of contingent events, generating unit dispatch, contingency remedial actions, load shedding practices, demand-side management, and equipment failure modes;

wherein step (b) involves a consideration of economic cost of contingencies and economic value of service, said economic cost of contingencies including the cost of unavailability of electric power due to an outage of an element of the power system, and said value of service including the value to a customer of uninterrupted electric power; and

wherein contingencies are selected on the basis of a combination of a ranking of contingency severity and a probability of occurrence based on equipment statistics, said contingencies including transmission line overload, transformer overload, voltage above or below prespecified limits, busbar isolation, system islanding, and a reactive power requirement above an available level.

3. A computer-based interactive method for assessing the reliability of power systems, comprising the steps of:

(a) developing an analytical model of the power system; and

(b) determining the effect on reliability of at least one of the following;

system additions, design alternatives, maintenance practices, substation configurations, and spare parts policies; and

further comprising a substation layout optimization step comprising the following substeps;

inputting an optimization objective, the layout of a substation, and the cost for equipment and maintenance associated with the substation layout;

determining the cost (θ

c) of the substation;

modeling failure modes of equipment associated with said substation layout;

determining the effects and cost of equipment failures;

determining an optimum number and cost of spare equipment (sc);

determining reliability indices;

determining maintenance costs (mc);

determining the total cost of ownership (OC) of the substation; and

establishing an optimum station layout for the specified objective;

wherein step (b) involves a consideration of economic cost of contingencies and economic value of service, said economic cost of contingencies including the cost of unavailability of electric power due to an outage of an element of the power system, and said value of service including the value to a customer of uninterrupted electric power; and

wherein contingencies are selected on the basis of a combination of a ranking of contingency severity and a probability of occurrence based on equipment statistics, said contingencies including transmission line overload, transformer overload, voltage above or below prespecified limits, busbar isolation, system islanding, and a reactive power requirement above an available level.

4. A computer-based interactive method for assessing the reliability of power systems, comprising the steps of:

(a) developing an analytical model of the power system; and

(b) determining the effect on reliability of at least one of the following;

system additions, design alternatives, maintenance practices, substation configurations, and spare parts policies; and

further comprising an overall bulk system reliability analysis step comprising the following substeps;

determining a study objective, power system model, and equipment cost;

establishing a base-case system topology;

modeling a system load;

defining a contingency list;

processing a first contingency on said list;

determining new operating conditions;

determining whether there are any violations and, if so, modeling relief actions and the cost of relief actions;

determining reliability indices;

determining the overall system cost for both equipment and contingency effects; and

establishing one or more of the following;

best alternative, indices, effect of wheeling, effect of operating practices, overall cost of alternatives;

wherein step (b) involves a consideration of economic cost of contingencies and economic value of service, said economic cost of contingencies including the cost of unavailability of electric power due to an outage of an element of the power system, and said value of service including the value to a customer of uninterrupted electric power; and

wherein contingencies are selected on the basis of a combination of a ranking of contingency severity and a probability of occurrence based on equipment statistics, said contingencies including transmission line overload, transformer overload, voltage above or below prespecified limits, busbar isolation, system islanding, and a reactive power requirement above an available level.

5. A method as recited in claim 4, wherein said violations include transmission line overloads, transformer overloads, voltages below or above specified limits, busbar isolations, system islanding, and reactive power requirements above the available levels.

6. A method as recited in claim 4, wherein said study objective includes a member of the following group:

a determination of reliability indices, a determination of the effect of wheeling, an analysis of alternatives, an evaluation of new equipment, an evaluation of operating practices, and an overall system cost determination.

7. A method as recited in claim 4, wherein said step of modeling relief actions and the cost of relief actions comprises determining a particular violation type and then performing at least one of the following substeps:

if the violation type is an overload violation;

re-dispatching generation, determining a new generating cost, determining whether there is still an overload violation and, if so, determining the optimum location and amount of load shedding and shedding the real amount of load;

if the violation type is a voltage violation;

reducing the voltage, determining whether there is still an overload violation and, if so, determining the optimum location and amount of load shedding and shedding the real amount of load;

if the violation type is a reactive power violation, determining the amount of violation; and

if the violation type is an islanding violation, adjusting the load and generation and then solving each island and relieving the violation;

wherein step (b) involves a consideration of economic cost of contingencies and economic value of service, said economic cost of contingencies including the cost of unavailability of electric power due to an outage of an element of the power system, and said value of service including the value to a customer of uninterrupted electric power; and

wherein contingencies are selected on the basis of a combination of a ranking of contingency severity and a probability of occurrence based on equipment statistics, said contingencies including transmission line overload, transformer overload, voltage above or below prespecified limits, busbar isolation, system islanding, and a reactive power requirement above an available level.

8. A computer-based interactive system for assessing the reliability of power systems, comprising:

(a) means for developing an analytical model of the power system; and

(b) means for determining the effect on reliability of the following;

system additions, design alternatives, maintenance practices, substation configurations, and spare parts policies;

wherein step (b) involves a consideration of economic cost of contingencies and economic value of service, said economic cost of contingencies including the cost of unavailability of electric power due to an outage of an element of the power system, and said value of service including the value to a customer of uninterrupted electric power; and

wherein contingencies are selected on the basis of a combination of a ranking of contingency severity and a probability of occurrence based on equipment statistics, said contingencies including transmission line overload, transformer overload, voltage above or below prespecified limits, busbar isolation, system islanding, and a reactive power requirement above an available level.

9. A computer-based interactive system for assessing the reliability of power systems, comprising:

(a) means for developing an analytical model of the power system; and

(b) means for determining the effect on reliability of at least one of the following;

system additions, design alternatives, maintenance practices, substation configurations, and spare part policies;

wherein the model includes load characteristics, demand projections, voltage profiles, energy and operating constraints, operator and automatic responses to the occurrence of contingent events, generating unit dispatch, contingency remedial actions, load shedding practices, demand-side management, and equipment failure modes;

wherein step (b) involves a consideration of economic cost of contingencies and economic value of service, said economic cost of contingencies including the cost of unavailability of electric power due to an outage of an element of the power system, and said value of service including the value to a customer of uninterrupted electric power; and

wherein contingencies are selected on the basis of a combination of a ranking of contingency severity and a probability of occurrence based on equipment statistics, said contingencies including transmission line overload, transformer overload, voltage above or below prespecified limits, busbar isolation, system islanding, and a reactive power requirement above an available level.

10. A computer-based interactive system for assessing the reliability of power systems, comprising:

(a) means for developing an analytical model of the power system; and

(b) means for determining the effect on reliability of at least one of the following;

system additions, design alternatives, maintenance practices, substation configurations, and spare part policies; and

further comprising a substation layout optimization means for performing the following substeps;

inputting an optimization objective, the layout of a substation, and the cost for equipment and maintenance associated with the substation layout;

determining the cost (θ

c) of the substation;

modeling failure modes of equipment associated with said substation layout;

determining the effects and cost of equipment failures;

determining an optimum number and cost of spare equipment (sc);

determining reliability indices;

determining maintenance costs (mc);

determining the total cost of ownership (OC) of the substation; and

establishing an optimum station layout for the specified objectives;

wherein step (b) involves a consideration of economic cost of contingencies and economic value of service, said economic cost of contingencies including the cost of unavailability of electric power due to an outage of an element of the power system, and said value of service including the value to a customer of uninterrupted electric power; and

wherein contingencies are selected on the basis of a combination of a ranking of contingency severity and a probability of occurrence based on equipment statistics, said contingencies including transmission line overload, transformer overload, voltage above or below prespecified limits, busbar isolation, system islanding, and a reactive power requirement above an available level.

11. A computer-based interactive system for assessing the reliability of power systems, comprising:

(a) means for developing an analytical model of the power system; and

(b) means for determining the effect on reliability of at least one of the following;

system additions, design alternatives, maintenance practices, substation configurations, and spare part policies; and

further comprising an overall bulk system reliability analysis means for performing the following substeps;

determining a study objective, power system model, and equipment cost;

establishing a base-case system topology;

modeling a system load;

defining a contingency list;

processing a first contingency on said list;

determining new operating conditions;

determining whether there are any violations and, if so, modeling relief actions and the cost of relief actions;

determining reliability indices;

determining the overall system cost for both equipment and contingency effects; and

establishing one or more of the following;

best alternative, indices, effect of wheeling, effect of operating practices, overall cost of alternative;

wherein step (b) involves a consideration of economic cost of contingencies and economic value of service, said economic cost of contingencies including the cost of unavailability of electric power due to an outage of an element of the power system, and said value of service including the value to a customer of uninterrupted electric power; and

wherein contingencies are selected on the basis of a combination of a ranking of contingency severity and a probability of occurrence based on equipment statistics, said contingencies including transmission line overload, transformer overload, voltage above or below prespecified limits, busbar isolation, system islanding, and a reactive power requirement above an available level.

12. A system as recited in claim 11, wherein said violations include transmission line overloads, transformer overloads, voltages below or above specified limits, busbar isolations, system islanding, and reactive power requirements above the available levels.

13. A system as recited in claim 11, wherein said study objective includes a member of the following group:

a determination of reliability indices, a determination of the effect of wheeling, an analysis of alternatives, an evaluation of new equipment, an evaluation of operating practices, and an overall system cost determination.

14. A system as recited in claim 11, wherein the means for modeling relief actions and the cost of relief actions comprises means for determining a particular violation type and then performing at least one of the following substeps:

if the violation type is an overload violation;

re-dispatching generation, determining a new generating cost, determining whether there is still an overload violation and, if so, determining the optimum location and amount of load shedding and shedding the real amount of load;

if the violation type is a voltage violation;

reducing the voltage, determining whether there is still an overload violation and, if so, determining the optimum location and amount of load shedding and shedding the real amount of load;

if the violation type is a reactive power violation, determining the amount of violation; and

if the violation type is an islanding violation, adjusting the load and generation and then solving each island and relieving the violations;

wherein step (b) involves a consideration of economic cost of contingencies and economic value of service, said economic cost of contingencies including the cost of unavailability of electric power due to an outage of an element of the power system, and said value of service including the value to a customer of uninterrupted electric power; and

wherein contingencies are selected on the basis of a combination of a ranking of contingency severity and a probability of occurrence based on equipment statistics, said contingencies including transmission line overload, transformer overload, voltage above or below prespecified limits, busbar isolation, system islanding, and a reactive power requirement above an available level.

15. A software-based tool for use by an electric utility in planning and operation of its power system, comprising:

(a) means for prioritizing system design alternatives based on economic cost, severity and probability of occurrence associated with a prescribed set of contingencies resulting in unavailability of electric power due to an outage of an element of the power system;

(b) means for developing an analytical model of the power system; and

(c) means for determining the effect on system reliability and cost of the following;

system additions, design alternatives, maintenance practices, substation configurations, and spare parts policies.

16. A tool as recited in claim 15, wherein said prescribed set of contingencies includes at least one member of the group consisting of transmission line overload, transformer overload, voltage above or below prespecified limits, busbar isolation, system islanding, and a reactive power requirement above an available level.