LasVegas2003 Rao SRP Presentation

8/21/2019 LasVegas2003 Rao SRP Presentation

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SRP Voltage Sag Index Methodology – Experience and FAQs

Rao Thallam and Kris Koellner

IEEE PES P1564 TF MeetingLas Vegas, 1/28/2003


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IEEE PE Review – July 2001

! “While most utilities can quotereliability numbers ……..; they

cannot provide a measure ofperformance for the quality ofpower supply”

Don Volzka, PES President


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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 exponentialrelationship to voltage

! Single index based on integral of voltagesquared and duration – Convenient Index


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Voltage Sag Energy, E VS

100]1[ 2

2

xdt V

V

nom

t VS !−=Ε


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Sag Energy Index

! For a given location and period

"iiVS E _


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System Average Sag EnergyIndex

N

SEI

N "


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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 sagfrequency.

! SSI – Sag Severity Index! Analogous to “CAIDI”, takes into account voltage sag

magnitude and duration.

SEI = SCI x SSI = " etcmonitor month SE ,,


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Sample Sag EnergyCalculations

If the phase energy values are 60, 90, and 90 and the duration of the event was 10cycles (.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 caseevent 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


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Sag Event Frequency Index

At a particular location and period(month or year)

= Number of qualified sag events at thatlocation and period


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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


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Qualifying Events

! Voltage Must be < 90%! Aggregation Time: 10 minutes

!

Event Duration limited to 15 cycles! Energy > 100, = 100

! Outages not included


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Data for 1999 - 2002

1999 2000 2001 2002

No. of Monitors 25 36 43 57Sag Events (


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SSCI(Severe Sag Count Index)

SCI(Sag Count Index)

SEI(Sag Energy Index)

SSI

(Sag Severity Index)


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Installed PQ Monitors (57) *

MC (2)

SR (3)

SYY (4)

CEM (2)

PIO (2)

BS (3)

GEN (2)

PK (3)

GL (3)

CE

MIP (2)

WER (2)

NO (2)

• Includes 3 monitors at PV sub in the Eastern Mining Area• Dashed areas indicate 69kV islands

MEY

WA (2)

TVH

Future PQ Monitors, FY2002/03 (1)

EV (2)

VA (3)

CLS

STR

PG

FW (2)

PV (3) [115kV]

CAHE (3)

LE SS

RO (2)

GR BL

SEI > 35+

25 < SEI < 34

20 < SEI < 24

12 < SEI < 19

SEI < 11

Sag Energy Index (SEI)

SEI = 31.8

SEI = 29.4

SEI = 7.0SEI = 9.8

SEI = 7.7

SEI = 10.3

SEI = 17.3

SEI = 6.7

SEI = 10.2

SEI = 12.8 SEI = 6.7

SEI = 13.0

SEI = 8.2

SEI = 23.7 SEI = 23.0

SEI = 10.8 SEI = 39.1

SEI = 17.0

SEI = 44.0

SEI = 14.8

SEI = 9.2

SEI = 7.9

SEI = 10.1

SEI = 8.8

SEI = 10.3

SEI = 5.7

SEI = 8.3

SEI = 9.5

SEI = 8.4

SRP Power Quality

Monitoring System, 2002


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Average SEI (CY2000)

! Dedicated industrial substation = 12.9

!

Residential 69kV substation = 18.9


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Correlation to C & I CustomerComplaints

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 2 0 0 0

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

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

E v e n t S e v e r i t y


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Sag Energy - FAQs

! Where do you get sag energy data forevents?

! What if PML Monitors are not used?!

Product of average sag voltage squared timesduration 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 ?


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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)


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Conclusions

! SRP installed monitors at selected locationsfor benchmarking and quantify power quality

! 57 Monitors in 2002

! Power Quality Index based on sag energydeveloped

! Good correlation with customers’ PQ concerns

! Results available for four years

LasVegas2003 Rao SRP Presentation

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