Frankfurt (Germany), 6-9 June 2011 Ying Wang – China – Session2– Paper 0587 Voltage Sag Frequency Assessment Considering Customer Satisfaction Degree Ying Wang Sichuan University,China

Frankfurt (Germany), 6-9 June 2011 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

Frankfurt (Germany), 6-9 June 2011 What is purpose of the utilities? For money?Supply light or heat? Power the machines?

Frankfurt (Germany), 6-9 June 2011 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) ?

Frankfurt (Germany), 6-9 June 2011 Voltage sag classical assessment methods 1 2 Statistic method Modeling method reliabledirect Long monitoringCostly installation Analytical method Fuzzy method Probabillity method Other uncertainty method

Frankfurt (Germany), 6-9 June 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:

Frankfurt (Germany), 6-9 June Customer Satisfaction degree (CSD)and its Interval Characteristic  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.

Frankfurt (Germany), 6-9 June 2011 Equipment types U min (%) U max (%) T min (ms) T max (ms) PLC ASD PC Customer Satisfaction degree (CSD)and its Interval Characteristic Tab. 1 the uncertain ranges of sensitive equipments B. Description of the contents satisfaction area S%=100 unsatisfaction area S%=0 uncertainty area S%=[0,100 ]

Frankfurt (Germany), 6-9 June 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:

Frankfurt (Germany), 6-9 June Proposed Analytical Method A. Critical fault location B. Un- satisfaction area C. Assessment of Voltage Sag Frequency Proposed Analytical Method

Frankfurt (Germany), 6-9 June A. Critical fault location V th is the limit voltage, The fault position x crit is the critical fault point Using Newton iteration method, the iteration equation is: where the x n, x n+1 are iteration values

Frankfurt (Germany), 6-9 June 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” Step I Step II Step III Step IV 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.

Frankfurt (Germany), 6-9 June 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 δ j and l j are the fault rate and fault line length in customer un- satisfaction area; n is the bus number.

Frankfurt (Germany), 6-9 June Case Studies A five-bus power system shown in the Figure Tab.2 Voltage sags per year at various busses Buss Number Proposed Method Fault Positions Method P=10P=100P= Buss Number Proposed Method Secant Iteration Method Tab.3 The numbers of iteration at various busses

Frankfurt (Germany), 6-9 June Case Studies The simulated system shown in Figure. It consists of 6 generator units, 30 buses interconnected by 37 lines and 4 transformers.

Frankfurt (Germany), 6-9 June Case Studies Buss Number PCPLCASD Monte Carlo Simulation Proposed Method Monte Carlo Simulation Proposed Method Monte Carlo Simulation Proposed Method 7 [5.2848, ] [5.2767, ] [2.6157, ] [2.5829, ] [8.4264, ] [8.4242, ] 15 [1.6674, ] [1.6521, ] [0.9309, ] [0.9107, ] [5.5859, ] [5.5851, ] 21 [3.4316, ] [3.4297, ] [1.5520, ] [1.5481, ] [8.2879, ] [8.2822, ] 26 [6.5614, ] [6.5612, ] [1.6654, ] [1.6478, ] [12.367, ] [12.358, ] 30 [8.5904, ] [8.5902, ] [4.9952, ] [4.9606, ] [12.408, ] [12.400, ] Tab.4 Voltage sags per year for different assessment methods

Frankfurt (Germany), 6-9 June Conclusions interval data of CSD CSD & customers correct and suitable  Interval data of CSD identifies the customer un- satisfaction area by an analytic method.  It is adaptive for radical network and meshed networks.  Simulation results have proved that the proposed method is correct and suitable for practical applications.  CSD can reflect how much the customers are influenced by the voltage sag.

Frankfurt (Germany), 6-9 June 2011