If two heavily loaded transmission lines trip and cause islanding, what is the likely impact on Interconnection frequency?

When two heavily loaded transmission lines trip and cause islanding, it results in a section of the power grid becoming electrically isolated from the rest of the system. In such situations, the generation and load within the isolated area may no longer be balanced.

Typically, if lines trip under heavy load conditions, there is a potential for a sudden drop in generation relative to the load. As generators are disconnected and cannot respond to the change in demand effectively due to the isolation, the excess load that remains can cause a shift in frequency. If the generation is not sufficient to meet the load, the interconnection frequency generally decreases due to the imbalance.

However, if the scenario implies that the remaining generators within the island are still producing at or above their output levels and compensating for the tripped load, the interconnection frequency will likely increase because the isolated operation allows generators to function without the previous system constraints.

Thus, the correct answer reflects the likelihood that frequency will rise in such a scenario following the independence achieved by islanding, as generation may outstrip load in the isolated segment, leading to an increase in frequency compared to the larger interconnection's previous operational levels.