What measurement is used for power flow data between balancing authorities?

The correct answer is tie-line metering, which involves measuring the actual power flow on the transmission lines (or tie-lines) that connect different balancing authorities. This measurement is crucial for ensuring the reliability and stability of the electric power system. By monitoring the flow of electricity across these interconnections, balancing authorities can balance supply and demand, manage reserves, and ensure that the power is delivered where it is needed.

Tie-line metering helps in verifying the interchange transactions, enabling coordination among different regions' electric systems. Accurate tie-line metering data is essential for settlement purposes, where the amount of energy exchanged between balancing authorities is recorded and billed appropriately.

In contrast, options such as interchange refer to the agreements or arrangements between balancing authorities regarding the transfer of power, and transactions are broader in scope, including all types of power trades and sales. Oasis, while related to the scheduling of transmission resources, does not specifically refer to the measurement of power flow. Therefore, the emphasis on direct measurements of power flow between balancing authorities clearly highlights the significance of tie-line metering in power system operations.