Ying Wang – China – Session2 – Paper 0587

1. Voltage Sag Frequency Assessment Considering Customer Satisfaction Degree Ying Wang Sichuan University ,China E-mail:tuantuan1125@126.com Ying Wang – China – Session2– Paper 0587

2. Contents 1. Introduction 2. Customer Satisfaction degree and its Interval Characteristic 3. Voltage Sag Assessment Under Interval Measure 4. Proposed Analytical Method 5. Case Studies 6. Conclusions

3. What is purpose of the utilities? Power the machines? For money? Supply light or heat?

4. purpose To meet customer satisfaction is the main concern for the utilities and customers Especially, when smart grid becomes a household name What is customer satisfaction degree (CSD) ?

5. direct reliable 1 Statistic method Long monitoring Costly installation Analytical method 2 Probabillity method Modeling method Fuzzy method Other uncertainty method Voltage sag classical assessment methods

6. 2. Customer Satisfaction degree (CSD)and its Interval Characteristic Sets the total operation time is Tt; the normal operation time as Ts; the abnormal operation time as Tc; Tt= Ts + Tc, The CSD presented by S % is:

7. presented by an interval data • based on the upper and lower thresholds of equipment voltage tolerance. CSD varies in a range • outside the curve 1--- operates normally • inside curve 2 ---un-satisfaction area • between the curve 1 and 2 is the uncertainty area. 2. Customer Satisfaction degree (CSD)and its Interval Characteristic

8. 2. Customer Satisfaction degree (CSD)and its Interval Characteristic Tab. 1 the uncertain ranges of sensitive equipments satisfaction area S%=100 B. Description of the contents unsatisfaction area S%=0 uncertainty area S%=[0,100 ]

9. 3. Voltage Sag Assessment Under Interval Measure where, and are pre-fault voltage at bus m and n. The voltage sag frequency is an interval range depending on CSD. The interval number of voltage sag is:

10. 4. Proposed Analytical Method A. Critical fault location B. Un-satisfaction area C. Assessment of Voltage Sag Frequency Proposed Analytical Method

11. 4-A. Critical fault location Vth is the limit voltage , The fault position xcritis the critical fault point Using Newton iteration method, the iteration equation is: where the xn, xn+1 are iteration values

12. Step I Step II Step III Step IV 4-B. Un-satisfaction area VL is short for “voltage limit ”,VSM is short for “voltage sag magnitude ” SA is short for “satisfaction area”, U-SA is short for“ un-satisfaction area” if the VL is less than the VSM both in the fault line beginning and the end, the bus is in the SA. if the VL is more than the VSM in all the point , the bus is in the U-SA. the VL is between the VSM in the bus beginning and the end, there is a critical fault point and the line is partly in the U-SA. if the VL is less than the maximum in all the point, and more than the VSM both in the beginning and the end, there are two critical fault points and the line have two parts in the U-SA.

13. 4-C. Assessment of Voltage Sag Frequency Based on Un-satisfaction area Uniform distribution of fault position along the transmission line was assumed, the sag frequency is: where δjand ljare the fault rate and fault line length in customer un-satisfaction area; n is the bus number.

14. 5. Case Studies A five-bus power system shown in the Figure Tab.2 Voltage sags per year at various busses Tab.3 The numbers of iteration at various busses

15. 5. Case Studies The simulated system shown in Figure. It consists of 6 generator units, 30 buses interconnected by 37 lines and 4 transformers.

16. 5. Case Studies Tab.4 Voltage sags per year for different assessment methods

17. 6. Conclusions • Interval data of CSD identifies the customer un-satisfaction area by an analytic method. • It is adaptive for radical network and meshed networks. interval data of CSD CSD & customers • CSD can reflect how much the customers are influenced by the voltage sag. correct and suitable • Simulation results have proved that the proposed method is correct and suitable for practical applications.

18. Thank you!