On Distribution Reliability Calculation

Transcription

1 On Distribution Reliability Calculation Impact of the Smart Grid on Bulk System Reliability Workshop Roger Dugan Sr. Technical Executive Manchester University 8 Dec 2011

2 Standard Reliability Indices Five of the standard sustained interruption reliability indices are computed by predictive reliability algorithms in distribution system analysis programs: SAIDI CAIDI SAIFI CAIFI ASAI But are these sufficient measures? They apply to 1-5 min interruptions 2

3 An Important Reliability Question What Do Customers Here See? 480 V 120/208 V 3

4 Service Quality Indices Mark McGranaghan, 2006 IEEE IAS Rural Electric Power Conference, April 10, 2006 Service Quality Index Example Application, EPRI, Palo Alto, CA: w/ Karen Forsten A consistent framework for characterizing service quality and reliability Based on Cost Uses a concept of economic impact on customers for different types of disturbances combined into a service quality index 4

5 Site vs. System Total Number of Momentary Interruptions per Year SYSTEM 100% 90% of Excceding X-Axis Va Probability o 80% 70% 60% 50% 40% 30% 20% 100% Average Momentary Interruptions per Year 95% Confidence Interval Bands 10% 90% 0% 80% Number of Momentary Interruptions 70% Probability of Exceeding X-Ax Axis Va 60% 50% 40% 30% 20% 10% 0% Number of Momentary Interruptions Proba bability of Excceding X-Axis Va 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% Total Number of Momentary Interruptions per Year 95% Confidence Interval Bands SITE 5 0% Number of Momentary Interruptions

6 SARFI where N i SARFI x N X = rms voltage threshold. Any positive value is possible. However, some of the more common values include 140, 120, 110, 90, 80, 70, 50, and 10. N i = Number of customers experiencing voltage deviations with magnitudes above X% for X >100 or below X% for X <100 due to measurement event i N T = Total number of customers served from the section of the system to be assessed T 6

7 Process Apply Faults in Proportion to failure rate (Could be more than one at a bus) 480 V 120/208 V Run 50,000 cases and normalize the results. Simulate protective device behavior and capture voltages at load points in a monitor. 7

8 Configuration V 480-volt Expected Distribution of Voltages f Samples Number o Number of Samples Cumulative Percentage 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% Percentage Cumulative Voltage (pu) 0% 8

9 Configuration 1 120/208 V 208-volt Expected Distribution of Voltages Number of Samples Number of Samples Cumulative Percentage 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% Cumulativ ve Percentag ge Voltage (pu) 0% 9

10 SARFI Results SARFI Level (480-V V LN ) Percentage of Events (at or below this level) SARFI % SARFI % SARFI % SARFI % SARFI % SARFI Level (208-V VVV LN or 480 Percentage of Events (at or V V LL ) below this level) SARFI % SARFI % SARFI % SARFI % SARFI % 10

11 Configuration V f Samples Number o volt Expected Distribution of Voltages - Normal Configuration Number of Samples Cumulative Percentage 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% Percentage Cumulative 0 0% Voltage (pu) 11

12 Configuration 2-120/208 V Number of Samples volt Expected Distribution of Voltages - Normal Configuration Number of Samples Cumulative Percentage 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% Cumulative Percentage 0 0% Voltage (pu) 12

13 SARFI Results SARFI Level (480-VV V LN ) Percentage of Events (at or below this level) SARFI % SARFI % SARFI % SARFI % SARFI % SARFI Level (208-V V LN or 480 V V LL ) Percentage of Events (at or below this level) SARFI % SARFI % SARFI % SARFI % SARFI % 13

14 Distributed ib t Generation on Distribution ib ti 14

15 DG and Reliability Distribution engineers typically are concerned that DG will degrade the reliability Therefore, DG disconnects at first sign of trouble Bulk power system needs DG to hang in there Low-voltage ride through Biggest complaint I get: A blink on the power system knocks the DG off line Many events are 5-6 cycle faults on Bulk Power System Whose reliability is it? 15

16 ARi Risk-Based kb Approach For Planning for DG and DR A Different View of Reliability 16

17 Basic Concepts 17

18 Annual LoadShape 18

19 Annual Demand Shape Power Energy 19

20 Energy At Risk of Being Unserved Most of the year, we can simply operate a switch and reconfigure after an N-1 event (major component failure) 20

21 Evaluating Impact of DG on EEN Incremental Capacity How much more load can we serve with the same risk of unserved energy as doing nothing? 21

22 Together Shaping the Future of Electricity 22