As for the skill level, that is, the senior workers, technicians and senior technicians you mentioned, I can provide the following reference:
1. If your province has direct evaluation, you can apply for direct evaluation of senior workers after you get the salary next year. If a senior engineer has worked for three years, he can apply for an appraisal technician. Or you can directly identify technicians after four years as assistants or engineers, that is, the so-called "double certificates"-technicians and engineers;
2. If there is no direct appraisal regulation in your province, you may have to attend relevant training before you can declare senior workers and technicians. As for the fixed number of years, it is similar to the first one mentioned above, except that the training in the middle will waste some time.
As for the training within the system you asked upstairs, there are other trainings, depending on your local superior department, which are generally recognized by provincial companies. As far as I know, some places also recognize maintenance electrician technicians in society, but they do not enjoy the treatment of electric power industry technicians in terms of salary; As for the difficulty you mentioned, for you, the theoretical examination, that is, the examination database, can certainly cope. As long as you pay attention to it, the difficulty may lie in your operation of the exam. You don't know what kind of work you are engaged in, but as long as you pay attention to it, it will be no problem.
Friends wish you success, hehe, just need time.