To mitigate a transmission line that reaches its System Operating Limit due to heavy power transfer, what is the best action?

The best action for mitigating a transmission line that reaches its System Operating Limit due to heavy power transfer is to put parallel lines in service. This approach effectively increases the overall capacity of the transmission system. When a transmission line is overloaded, adding parallel lines distributes the electrical load among multiple paths, reducing the stress on the original line. This can prevent overheating and ensure that the transmission system can continue operating safely and efficiently.

Parallel lines also enhance reliability and redundancy in the system. If one line goes out of service for maintenance or due to a fault, the other lines can still handle the power transfer, maintaining system stability. This strategy is particularly important in high-load scenarios, where capacity needs exceed what a single line can safely carry.

In contrast, while adding capacitors or reactors can help with voltage regulation or reactive power management, they do not directly increase the thermal capacity of the line to manage heavy power transfer. Increasing schedules from the direction of the power flow might lead to further stress on the existing lines, potentially exacerbating the issue rather than resolving it. Therefore, utilizing parallel lines is the most effective and comprehensive solution to mitigate the overload situation.