A major transmission line has become overloaded, and the transmission operator has taken actions to unload the line. However, the overload persists, and the equipment is now in imminent danger of damage. What is the next action to take?

A. Separate from the Interconnection
B. Disconnect the overloaded line and notify the RC and affected Transmission Operators.
C. Request a Transmission loading relief procedure
D. Request permission from the RC to open the line.

The most immediate action to take when a transmission line is overloaded and in danger is to disconnect it and inform the RC and affected Transmission Operators, prioritizing grid safety.

Explanation:

When a major transmission line becomes overloaded and remains so despite attempts to unload it, presenting imminent danger of damage to the equipment, the most immediate and effective action to take is to disconnect the overloaded line and notify the Reliability Coordinator (RC) and affected Transmission Operators. This action helps prevent further damage to the grid infrastructure and ensures safety. Other steps such as separating from the Interconnection or requesting a Transmission Loading Relief procedure might be considered in specific scenarios, but the priority is to mitigate the immediate risk to the transmission line and broader grid by disconnecting it and informing relevant parties.