Resiliency of Capacity Benefit Margin (CBM) and Available Transfer Capacity (ATC) metrics
- Nov 23, 2020 5:03 pm GMTNov 23, 2020 12:48 pm GMT
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I am struck by the resiliency of some of the transmission capacity concepts such as Capacity Benefit Margin (CBM), ATC, and Available Flowgate Capacity. Before the energy market, some capacity on the transmission lines and key interfaces was set aside for reliability and emergency purposes. That margin on the system ensured when supplies were short, there is enough transmission reservation available for the generation to reach areas where it was needed. This is why we have a LOLE standard of 1 day in 10 years, showing how much transmission support was needed to maintain reliability before the firm load shed.
But with energy markets, at least for entities within a transmission provider - those margins need not be set aside. Because the reliability coordinator is responsible for balancing the supply and demand. The day ahead and real-time energy markets and forward-looking capacity markets fill that energy and capacity need. This is the reason why we have summer, winter, and long term reliability assessments both on resources and transmission.
Since our US electric system continues to have pockets outside the organized markets such as southeast and west regions, even though there are active discussions underway on energy imbalance markets in both southeast and western regions - market to non-market flowgate coordination and market to market flowgate coordination continues to be relevant. Which makes the CBM, ATC and AFC concepts important.
NERC standards NERC MOD-001-1a and MOD-030-3 deal with the calculation of Available Transfer Capability.