SRP Voltage Sag Index Methodology Experience and FAQs

Transcription

1 SRP Voltage Sag Index Methodology Experience and FAQs Rao Thallam and Kris Koellner IEEE PES P1564 TF Meeting Las Vegas, 1/28/2003

2 IEEE PE Review July 2001! While most utilities can quote reliability numbers..; they cannot provide a measure of performance for the quality of power supply Don Volzka, PES President 2

3 Voltage Sag Realities! Magnitude varies during the event! Sag different in Three Phases! Impact of sag event is function of both voltage magnitude and duration! Impact on equipment is exponential relationship to voltage! Single index based on integral of voltage squared and duration Convenient Index 3

4 Voltage Sag Energy, E VS Ε VS = 2 V [ 1 t 2 V nom dt] x 100 4

5 Sag Energy Index! For a given location and period i E VS _ i 5

6 System Average Sag Energy Index SEI N N 6

7 Voltage Sag Index Definitions! SEI Sag Energy Index! Analogous to SAIDI, takes into account voltage sag frequency, magnitude, and duration.! SCI Sag Count Index! Analogous to SAIFI, takes into account voltage sag frequency.! SSI Sag Severity Index! Analogous to CAIDI, takes into account voltage sag magnitude and duration. SEI = SCI x SSI = month, monitor, etc SE 7

8 Sample Sag Energy Calculations If the phase energy values are 60, 90, and 90 and the duration of the event was 10 cycles (.166 seconds) the Sag Energy (SE) for that event would be: SE = [(100 60) + (100 90) + (100 90)] x [.166] SE = [(40) + (10) + (10)] x [.166] SE = [60] x [.166] SE = 9.96 SE is only calculated for events up to 15 cycles (.25 seconds) so the worst case event would be an outage on all three phases for 15 cycles or longer. An outage is equivalent to phase energy values of 0, 0, and 0. The SE in this case would be: SE = [(100 0) + (100 0) + (100 0)] x [.25] SE = [(100) + (100) + (100)] x [.25] SE = [300] x [.25] SE = 75 8

9 Sag Event Frequency Index At a particular location and period (month or year) = Number of qualified sag events at that location and period 9

10 System Sag Count Index Total Number of Qualified voltage Sag events SCI = Number of monitor locations Note: By dividing with number of monitor locations, data is normalized 10

11 Qualifying Events! Voltage Must be < 90%! Aggregation Time: 10 minutes! Event Duration limited to 15 cycles! Energy > 100, = 100! Outages not included 11

12 Data for No. of Monitors Sag Events (<0.9) Events after aggregation

13 SEI (Sag Energy Index) SCI (Sag Count Index) SSI (Sag Severity Index) SSCI (Severe Sag Count Index) 13

14 SRP Power Quality Monitoring System, 2002 PG SEI = 31.8 Sag Energy Index (SEI) SEI > < SEI < < SEI < < SEI < 19 SEI < 11 CA SEI = 44.0 STR EV (2) SEI = 6.7 VA (3) SEI = 29.4 BS (3) SEI = 9.2 SEI = 14.8 MIP (2) WER (2) TVH HE (3) SEI = 17.3 PIO (2) CLS RO (2) SEI = 7.0 SR (3) GL (3) CEM (2) PK (3) NO (2) SEI = 9.8 MEY FW (2) SEI = 10.8 SEI = 39.1 SEI = 10.1 SEI = 7.9 SEI = 10.2 SEI = 8.8 SEI = 8.3 SEI = 9.5 SEI = 10.3 MC (2) GR SEI = 12.8 SEI = 6.7 SEI = 5.7 SEI = 17.0 WA (2) SEI = 8.4 CE LE PV (3) [115kV] SEI = 8.2 SEI = 13.0 SEI = 23.7 SS SEI = 23.0 BL GEN (2) SEI = 7.7 Installed PQ Monitors (57) * Future PQ Monitors, FY2002/03 (1) Includes 3 monitors at PV sub in the Eastern Mining Area Dashed areas indicate 69kV islands SYY (4) SEI =

15 Average SEI (CY2000)! Dedicated industrial substation = 12.9! Residential 69kV substation =

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18 Correlation to C & I Customer Complaints L a r g e I n d u s t r i a l C u s t o m e r P o l w e r Q u a l i t y I s s u e s, C Y E v e n t S e v e r i t y J a n F e b M a r A p r i l M a y J u n e J u l y A u g u s t S e p t O c t N o v D e c M o n t h 18

19 Sag Energy - FAQs! Where do you get sag energy data for events?! What if PML Monitors are not used?! Product of average sag voltage squared times duration is a good approximation for integration. Error < 2 to 3%! Variation of number of monitor locations? Data is normalized! Aggregation time? 1 min or 10 min! SRP LIC Satisfaction Index? 19

20 X Results using Vavg^2/Vnom^2 rather than phase Energy Results are within +/- 10% towards the low end of the sag energy scale Maximum deviation at the upper end (longer, more severe events) 20

21 Conclusions! SRP installed monitors at selected locations for benchmarking and quantify power quality! 57 Monitors in 2002! Power Quality Index based on sag energy developed! Good correlation with customers PQ concerns! Results available for four years 21