Robert Broadwater EDD Blacksburg, Virginia

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2. 2 Economics of DG Generation DGs may sometimes be used to avoid large capital investments, often to solve problems that only exist for a short period

3. 3 Using DG to Correct Low Voltage

4. 4 Zoom In to DG Site

5. 5 DG Corrects Problem

6. 6 Hierarchical Control

7. 7 Control System

8. 8 Historical Measurements 8760 hourly kW, kVar measurements for some large customers 12 kWHr measurements for other loads Load research statistics are used to estimate kW, kVar loads

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10. 10 Distribution Transformer Models

11. 11 Customer Types

12. 12 Monthly kWHr Measurements

13. 13 Control System

14. 14 Scaling of Model Loads Some model loads are scaled to cause power flow results to match real-time measurements Non-scalable loads Load scaling restrictions

15. 15 Control System

16. 16 Control of Voltages and Currents No direct measurement of problems Use model to predict problems Use model to calculate generation levels needed to eliminate problems Low voltages Equipment overloads

17. 17 DG Control Features Control performed 24 X 7 Complete control calculation, including power flow, requires 1-2 seconds per circuit Calculates “just right” level of generation Takes into account constraints

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21. 21 Reliability for Time Varying Load As illustrated in this Figure, the estimated load of L_C32 fluctuates during the 24-hour period, and reaches its peak value around 6pm to 7pm, when most of people return home and turn on their electric utilities. Along with time, the variation of the reliability of line L_C1, which is reflected by its down time, is also illustrated in this figure. We can see that from 12am to 4pm, when the load in line L_C32 remains relatively low, the down time for line L_C1 stabilizes at 0.36Hr/Yr. When the load of line L_C32 rapidly grows in the evening, it triggers a dramatic increase in the down time, which jumps from 0.36Hr/Yr to 0.805Hr/Yr. After that summit period, from 6pm to 9pm, the down time of line L_C1 decreases to 0.36Hr/Yr again. This change of the reliability of line L_C1 with the variation of load in line L_C32 is because the reliability of depends on the availability of the alternative source. While the load in the adjacent circuit goes up to the point close to being over loaded, it has no remaining capability to support the original circuit any more. So the annual down time for LC1 significantly increases **Now we can see how change of the system loading impact the system reliability. As illustrated in this Figure, the estimated load of L_C32 fluctuates during the 24-hour period, and reaches its peak value around 6pm to 7pm, when most of people return home and turn on their electric utilities. Along with time, the variation of the reliability of line L_C1, which is reflected by its down time, is also illustrated in this figure. We can see that from 12am to 4pm, when the load in line L_C32 remains relatively low, the down time for line L_C1 stabilizes at 0.36Hr/Yr. When the load of line L_C32 rapidly grows in the evening, it triggers a dramatic increase in the down time, which jumps from 0.36Hr/Yr to 0.805Hr/Yr. After that summit period, from 6pm to 9pm, the down time of line L_C1 decreases to 0.36Hr/Yr again. This change of the reliability of line L_C1 with the variation of load in line L_C32 is because the reliability of depends on the availability of the alternative source. While the load in the adjacent circuit goes up to the point close to being over loaded, it has no remaining capability to support the original circuit any more. So the annual down time for LC1 significantly increases **Now we can see how change of the system loading impact the system reliability.

22. 22 Case Study The algorith we just discussed, are applied to this three-circuit system. These three circuits, C1, C2, C3, are supplied by substations Sub1, Sub2 and Sub3, respectively. Names of all the segments are also shown in this picture. This is a complex system with both residential and manufacturing customers. Different types of customers have various load patterns. The algorith we just discussed, are applied to this three-circuit system. These three circuits, C1, C2, C3, are supplied by substations Sub1, Sub2 and Sub3, respectively. Names of all the segments are also shown in this picture. This is a complex system with both residential and manufacturing customers. Different types of customers have various load patterns.

23. 23 Circuit Load and System Load Here we have a clear picture of the load curves of the entire system and individual circuits. The whole system has its lightest load around 3am, and peaks at 6pm. time points 3am, 6am, 12pm and 6pm are selected to conduct the reliability analysis and power loss calculation. Here we have a clear picture of the load curves of the entire system and individual circuits. The whole system has its lightest load around 3am, and peaks at 6pm. time points 3am, 6am, 12pm and 6pm are selected to conduct the reliability analysis and power loss calculation.

24. 24 Optimum Locations To minimize the power loss, the DG should be placed in segment C3_B6. When the system has a light to modest load, segment C1_B3 is the locations to improve the system reliability the most When the system has a heavy load, the DG should be sited in segment I_SW3 When the system is at maximum load, the DG should be sited in segment Island_SW1 of C3 to obtain the greatest reliability improvement. The results from two analyses are different. Let take a look at the normal working hours, From 9am to 5pm, segment I_SW3 is the optimal location for reliability enhancement, segment C3_ B6, the optimal location for loss reduction To minimize the power loss, the DG should be placed in segment C3_B6. When the system has a light to modest load, segment C1_B3 is the locations to improve the system reliability the most When the system has a heavy load, the DG should be sited in segment I_SW3 When the system is at maximum load, the DG should be sited in segment Island_SW1 of C3 to obtain the greatest reliability improvement. The results from two analyses are different. Let take a look at the normal working hours, From 9am to 5pm, segment I_SW3 is the optimal location for reliability enhancement, segment C3_ B6, the optimal location for loss reduction

25. 25 Analysis ResultsDG Effects on System Reliability and Loss This table indicates two DG placements for each time point. The first location is for the best reliability improvement, and the second location is for the minimum power loss. in previous research, it was noted that applying DG helps to enhance system reliability more during light load periods than during heavy load periods. This is because when a circuit is lightly loaded it has more spare capacity to support its neighboring circuits as an alternate source. This time,. 3pm is the time that the system has lightest demand. But the largest reliability improvement by adding DG at 12pm, when system load is heavy. This is because the different load conditions influence the reliability improvement by DGs. Previous work studied a system that has two circuits that have the same daily load curve. Thus, when both of the circuits have high demand, adding a DG to either one will not help much, because at such a condition both circuits do not have enough spare capacity to help their adjacent circuit in case of failure. This table indicates two DG placements for each time point. The first location is for the best reliability improvement, and the second location is for the minimum power loss. in previous research, it was noted that applying DG helps to enhance system reliability more during light load periods than during heavy load periods. This is because when a circuit is lightly loaded it has more spare capacity to support its neighboring circuits as an alternate source. This time,. 3pm is the time that the system has lightest demand. But the largest reliability improvement by adding DG at 12pm, when system load is heavy. This is because the different load conditions influence the reliability improvement by DGs. Previous work studied a system that has two circuits that have the same daily load curve. Thus, when both of the circuits have high demand, adding a DG to either one will not help much, because at such a condition both circuits do not have enough spare capacity to help their adjacent circuit in case of failure.

26. 26 Economic Considerations Assume 5 ¢ per kwHr 9am-5pm (1097kw – 975kw ) x 8hr x $.05 = $48.8 Let take a look at the normal working hours, From 9am to 5pm, segment I_SW3 is the optimal location for reliability enhancement, segment C3_ B6, the optimal location for loss reduction If the DG is put in segment I_SW3, instead of segment C3_ B6. Assume… according to the table shown in slide 15, moving the DG from segment C3_ B6 to I_SW3, SAIDISYS will be improved by 6.97%, how much this 6.97% reliability improvement is really worth? the fact is that For some customers, like hospitals, or some industry with continuous processing, such as food processing, the cost of power outages can be disastrous. Studies indicate that nationwide, power fluctuations cause annual losses of $12 billion to $ 26 billion [11]. So considering the economic impact, the reliability of the power system may often receive a higher priority than improved efficiency due to lower losses.Let take a look at the normal working hours, From 9am to 5pm, segment I_SW3 is the optimal location for reliability enhancement, segment C3_ B6, the optimal location for loss reduction If the DG is put in segment I_SW3, instead of segment C3_ B6. Assume… according to the table shown in slide 15, moving the DG from segment C3_ B6 to I_SW3, SAIDISYS will be improved by 6.97%, how much this 6.97% reliability improvement is really worth? the fact is that For some customers, like hospitals, or some industry with continuous processing, such as food processing, the cost of power outages can be disastrous. Studies indicate that nationwide, power fluctuations cause annual losses of $12 billion to $ 26 billion [11]. So considering the economic impact, the reliability of the power system may often receive a higher priority than improved efficiency due to lower losses.

27. 27 DG Placement for BestReliability If DGs are to be shut down when circuits experience outages, then DGs should be placed in circuits that have the lowest failure rates. If DGs can be operated as islands, then DGs should be placed in circuits that have the highest failure rates.

28. 28 Conclusions DG placement in a circuit DG placement in a system of circuits Optimal DG placement