2009 State of the Market Report
mitigation in the NCAs than in the BCAs, even though there are many more BCAs. Figure 86 shows the frequency and quantity of mitigation in the real-time market by month. Very little mitigation was imposed in the day-ahead market. This is expected because the day-ahead market is much less vulnerable to withholding due to the presence of virtual traders.
Figure 86: Real-Time Mitigation by Month 2008 – 2009
Hours Mitigated, NCA Hours Mitigated, BCA Average MW Mitigated
0 07 08 09 J F M A M J J A S O N D 07 08 09 J F M A M J J A S O N D Avg. BCA Avg. NCA
Real-time NCA and BCA mitigation was exceedingly rare in 2009, dropping 98 percent and 74 percent respectively from 2008. Only 5 BCA and 3 NCA unit-hours of mitigation occurred, down from 17 and 122 unit-hours in 2008. This was generally due to lower levels of congestion, particularly into the NCAs. When mitigation did occur, the quantities mitigated were still substantial, averaging 193 MW and 73 MW per unit-hour for NCA and BCA mitigation respectively. Although mitigation was infrequent during 2009, the pivotal supplier analyses discussed earlier in this section continue to indicate that local market power is a significant concern. If exercised, local market power could have substantial economic and reliability consequences within the Midwest ISO market. Hence, market power mitigation measures remain essential.