Skip to comments.Power System Stability: How to Prevent Blackouts in the Open Access Era
Posted on 08/15/2003 9:58:20 AM PDT by Lessismore
In the summer of 1996, two major system disturbances occurred in the Western System Coordinating Council (WSCC) that resulted in partial blackouts and cost utilities and their customers several million dollars. Potential stability problems are still the most critical impediments to maximizing power transfers across system interconnections and must be considered in available transfer capability. Until recently, stability studies conducted by electric utilities focused primarily on transient angle stability. However, with the changing characteristics of power systems, other system stability problems, particularly voltage instability and undamped inter-area oscillations, have emerged as greater sources of concern. This was made abundantly clear from these two 1996 disturbances.
Maintaining system stability in a deregulated utility environment will present new challenges, as power systems are operated with a greater degree of uncertainty and a lower level of conservatism than in the past. If stability problems are accurately identified and properly mitigated, the economic gains to be realized can be enormous.
This two-day course, presented by two prominent experts in the field, will cover the different stability problems that are encountered by dispatchers and schedulers, as well as state-of-the-art analysis and mitigation techniques. Both presenters have written books on this subject for the Electric Power Research Institute (EPRI), and are skilled at presenting these complex issues in a straightforward format.
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Talk about a mild understatement. Apparently a whole lot of Quebec Hydro megawatts just dropped off of the NIMO grid, - meaning somebody up there really crowbarred it. The only reason Mongy County and DC didn't go down is because the guys at Chalk Point and Morgantown said "Not on my watch" and stepped out of the way. What is amazing is that the pressies and many bubblehead pols [Bill Richardson, Pataki, Bloomberg, et al] seem to think that the grid can be restarted in a minute or two. Using Manhattan as an example, every big transmission bus in the city has to be stripped of its load, verified as stripped, put on line and then loaded up piece by piece in total coordination with the x number of dispatchers and generators. It is a very complex operation and if it is buggered up at any point in the process then generators trip out and the process must be started from scratch. Another matter of interest which should soon come to light is the extent of the NIMO grid's dependence on Quebec Hydro. Don't know what it is but it is probably humungous.
We knew that ;-)
In 1980, I had the pleasure of observing an Arizona Public Service engineer tune the exciter for Cholla #4 [400MW coal-fired plant, Joe City, AZ]. For a techno-geek like me, it was almost orgasmic.
John and his team used a (new at the time) piece of Hewlett Packard test equipment called a structural dynamics analyzer, which was basically a souped-up Laplace transformer.
They used a pink noise source (rolls off at 6dB per octave) in the HP analyzer as an input to the exciter for the generator. This caused the generator to put out more or less power in response to the pink noise signal. The noise was highly attenuated so as not to be noticible to the system operators.
Then they installed a magnetic pickup tachometer on the main turbine shaft, discriminated the output to give an analog signal proportional to frequency deviation, and fed it back into the HP analyzer.
With the 400MW generator connected to the grid, they allowed this setup to integrate the extremely minor sub-synchronous (less than 60 Hz) variations in frequency. Over a period of about four days, they came up with a plot of the sub-synchronous resonant frequencies of the entire system - meaning the rotatating equipment at Cholla, the transmission lines, and all the other generators on that grid.
The HP analyzer produced a mathematical formula for the system, "inverted" it, and the exciter at Cholla was tuned to cancel out those peaks. Presto!
It was the neatest thing I have ever seen (with the possible exception of a space shuttle launch). God, those were the days (wiping a small tear from my eye)...