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A Grid-based View of Loads

Date: Thursday, June 28th, 2012

Location: SRP Information Services Building (ISB), 1600 N Priest Dr, Tempe, AZ 85281

Speaker: John Undrill, GE Energy

Topic: "A Grid-based View of Loads"

Engineers concerned with the security of the grid see load at the level of distribution substations.The key question they have asked for many years regarding loads is:
What does the load do when voltage and frequency vary by a few percent as the grid moves around after a fault in the transmission system.

Related issues, including the behavior of load during the few milliseconds of a fault were largely sidestepped, initially because of computing limitations, and later because the difficulty of getting data. Now however we are finding that we need to ask a range of questions much broader than we could have hoped to have answered as recently as five years ago:
What does the load do in the few milliseconds for which voltages are depressed by a fault?
Do large numbers of motors stall?
Do new-technology lamps extinguish?
What do electronic drives do?
What do loads do in the several seconds after a fault has been cleared and supply is restored?
Do motors restart when supply comes back?
Immediately, or after a delay?
What proportion of load would be deliberately disconnected by its direct controls?
Immediately, or after a delay?
What proportion of the load would be disconnected/reconnected by supervisory controls - such as building management systems?
At what voltage levels to these various things happen/not happen?

We are working intensively on models of load behavior that can be married into the large scale simulation programs used in grid analysis. We have good ability to model the physics of individual devices (things we can test in laboratories),
but our ability to model the collective behavior of loads is less well developed.

We need to improve our fund of information on load behavior, both as measured and recorded at the customer service entry level and as seen at feeder heads. We think that we should be listening to, and learning from, the power quality community.

Speaker Bio:
John Undrill started his career with GE in its Electric Utility Engineering Operation. After his early spell at GE he spent 16 years at Power Technologies Incorporated, moved on to co-found Electric Power Consultants, Inc, and then returned to GE when GE bought EPC. He has been involved in the analysis, testing, and commissioning of power system equipment for 47 years. A large part of his work has required him to understand the effect of load behavior on the stability and control performance of the bulk transmission grid. He is a Fellow of the IEEE and a member of the National Academy of Engineering.