IEEE P1564 Task Force on Voltage Sag Indices
IEEE PES Summer Meeting
July 17, 2001 – Vancouver CN
Meeting Minutes
Welcome and Introduction:
Mike Sheehan welcomed attendees and introduced Larry Morgan and Randy Collins who gave a short presentation on a Real Time Sag Detector.
Discussion
Math Bollen briefly reviewed the proposed 5 step process for developing Sag Indices and reported action taken at the IEEE P1159 meeting on Monday regarding the 1159.1 and 1159.2 work. During that meeting, it was decided to use the draft IEC 61000-4-30 as a basis for the new 1159.x document. Important for our working group is that this gives us a definition of magnitude and duration. It was decided to use the definition according to IEC 61000-4-30 as the basis for the 1564 document.
Dan Sabin has rewritten Chapter 5 of Draft 1.2 of the working group document. Math Bollen will include Dan's material in the next draft. A short discussion followed based on Dan's summary of his contribution.
It was suggested to explicitely include in the document the option of redefining the definition of SARFI. As an example: when the voltage tolerance of an installation is known SARFI can be redefined to give the number of potentially-disturbing events.
It was also suggested to differentiate between single-phase and three-phase events.
- Scott Peele presented an alternative way of obtaining voltage-sag indices from monitors. His utility uses fault current data to determine the number of faults per circuit mile. This gives, according to him, a better measure of the performance of the utility network. The number of voltage sags experienced by a customer can be calculated from the number of faults per circuit mile by using the methods described in Chapter 9 of the Gold Book and in IEEE 1346. It was noted that where monitoring data is not available, such methods may be an alternative means of obtaining voltage sag performance data.
His proposal resulted in an interesting and lively discussion. The main issue of the discussion was: there is no direct link between voltage-sag frequency and faults per circuit mile; and the customer is not interested in network performance but in sag frequencies.
It was suggested to add a chapter for the working group document on predicting sag indices from fault frequencies. Scott Peele volunteered to write a first draft.
The most meaningful expression of voltage sag data may be different for different users. Mike Sheehan will write a short discussion of who the intended index user is to be.
- Rao Thalum gave a presentation on the use of a Sag Energy Index based on data obtained from monitors installed at selected locations on the Salt River Project system. This presentation is included in these minutes. Rao showed an interesting correlation between the index and the number of customer complaints. Other utilities were encouraged to check for similar correlations with their indices. One issue resulting from discussion of Rao’s presentation is the appropriate aggregation time for sag index calculations.
- Jim Burke summarized the discussion from last meeting on using pre-event voltage or nominal voltage as a reference. He will provide a written discussion of the two options.
Action Items:
Math and Mike will update the working group document.
Scott Peele will write a first draft of the chapter on "predicting sag indices".
Mike will write a discussion of who the voltage sag index is intended for.
Jim Burke will write a discussion on reference voltage.
Working group members are encouraged to read and comment on the revised draft prior to the Winter Meeting.
Issues that need resolution
The aggregation time period to be used for voltage sag calculations needs to be defined.
Loss of information when moving from samples to system indices.
What and for whom is the index intended.
4. Determination of weighting factors used in obtaining system indices from site.
Time Line:
Math will incorporate Dan Sabin’s chapter in the P1546 draft by 9/20.
Draft will be to Russ by 9/27.
Russ will post draft on web and notify working group by 10/4.
Comments on draft are due back to Russ by 11/15.
Mike will prepare paper copies including comments to be distributed at the winter meeting.
Next meeting at IEEE PES Winter Meeting in New York.
Respectfully Submitted,
Dave Vannoy acting Secretary for Russ Ehrlich who home was waiting for baby #1 to arrive.