Reliability
We take our role in maintaining reliability seriously. In order to be successful, we must blend the right tools with an investment in the continuous education of our employees.
We determine the state of the system every 90 seconds using more than 240,000 points of information, allowing for greater visibility into system conditions, increased ability to quickly identify the most effective response, and better coordination of needed system maintenance.
Midwest ISO operators receive more than 100 hours of training a year. This training consists of a mix of classroom and hands-on simulation activities. Classroom topics range from Midwest ISO-specific procedures to industry concepts. Simulation activities include participation in one of the largest Emergency Procedures/Power System Restoration drills in the industry, with participation including Midwest ISO staff, member Balancing Authorities, and personnel from neighboring regions.
A quick response requires accurate information. The Midwest ISO processes system condition information every four seconds, resulting in appropriate signals being sent to generation owners in a timely manner.
This capability has resulted in quicker response to high demand situations. In the past, the Midwest ISO utilized the Transmission Loading Relief (TLR) procedure as the primary means to manage heavy use of the system. The results of this process are seen in about 30 minutes. Under the Midwest Market, the use of economic dispatch allows for relief of heavily loaded lines as part of the five-minute economic dispatch process.
The increase in data availability also means that our customers can perform necessary equipment maintenance throughout the year with the knowledge that the Midwest ISO's outage scheduling process ensures that the system will remain reliable. This ability allows maintenance to occur prior to key demand periods, such as the summer, and provides the flexibility to conduct emergency maintenance during high demand periods with the assurance that other effective options are available to meet the demand.
These mechanisms and systems are critical as electricity use continues to climb in the Midwest - going from a peak of 119,207 MW in 2004 to 136,520 MW in 2006.
In April 2005, a critical transmission line connecting Minnesota and Wisconsin was forced out of service due to a large fire. Member companies provided the Midwest ISO was provided with 15 minutes advance notice of the outage. Working with our members, Midwest ISO operators moved energy flows off the transmission lines and instructed quick-start generators to begin serving energy needs. These actions allowed the outage to occur with minimal impact on system reliability.
In March 2006 several storms moved across the Midwest, resulting in more than 25 transmission facilities being forced out of service. This resulted in loss of power for more than 70,000 customers across the Midwest. The Midwest ISO worked with impacted areas and adjacent areas to minimize the impact and provide directives based on information obtained as part of the Midwest ISO’s broad system visibility, resulting in providing the affected areas the opportunity to focus on restoring their systems in a reliable and timely manner.
| Tool |
Data Points |
Solve Time |
How Often Runs |
Purpose |
| State estimator |
230,000+ real–time measurements |
Every 90 seconds |
Continuously |
Look at current system conditions |
| Real–time contingency analysis |
9,000+ contingencies |
Less than two minutes |
Automatically every five minutes or immediately on demand |
Examine “what if” scenarios |
| Security Constrained Economic Dispatch |
1,400 + commercial pricing nodes |
Net Scheduled Interchange sent every four seconds, generator instructions sent every five minutes |
Every five minutes |
Adjust generator output based on lowest price, system conditions, and load |
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