I need help with a Engineering question. All explanations and answers will be used to help me learn.

Question-1 [10 Points]

What is the threshold level of renewable energy penetration (in percentage) at which the utilities are required to change their engineering and planning strategies?

Question-2 [20 Points]

Enumerate the impacts of large scale renewable penetration on the U.S transmission grid.

Question-3 [40 Points]

During the periods of high penetration, wind and solar energy have to be curtailed. What is the reason for doing this? Provide practical examples.

Question-4 [20 Points]

State the applications of energy storage for integrating intermittent renewable energy sources into the power system.

Note: Description should not exceed 3 pages for each question. The text should be in Century School, font size-12 with single spacing. You can include figures and tables.