When do you think it becomes necessary to create a second base line of the schedule?

Thank you Anisuddin for yuor excellent quesion and also thanks for Bini for his good dense answer.
The schedule base line is needed to act as a platform against which you can track out the progress of the project when it is started .
Depending on the intervals of time at which you check the progress of the project and to sea that you are ahead or behind,the base line should be change at each periodic updating of the project and the present state must be adopted as a baseline fo the next one.
Thank you Best regards.

Second baseline would be needed for evaluating the current project against a previous stage in the program which could be a quarter or month or a week after the project started and progressed also to have a periodic analysis of the project

i think will be important if there is varation order or a change in the scope of work