How do you troubleshoot and maintain electrical equipment and systems in complex facilities?

Firstly, should check entire hardware components configuration and implementaion on electrical system, and then stepwise test software functions to find any problem, and then suggest an optimal solution for reliable system performance satisfaction.

Excluding PPE issues (which I think is a separate issue); Think big picture and mentally divide system into functional parts. Then, list potential functional parts that could possibly cause the observed problems and begin testing to prove each function as good (or bad). Once you narrow down to the problem area, divide that into sub-systems or sub-functions and use the same approach, and keep zooming in until you have identified the faulty component. It is important to take the time to perform strategic testing and to record & analyze results. Avoid the temptation to swap parts blindly as this often introduces new faults (misconfigurations, miswiring, etc.) that further complicate troubleshooting efforts.

Ensuring you understand the equipment and procedures, and that you find the official forms, spec sheets, config sheets, etc., so that the equipment is properly configured and setup. This step is too often simply 'guesswork' and results in problems including reduced safety margins or defeated protections. For example I saw an instance where a Tech installed a safety level transmitter with extremely long damping time without knowing it. The result was that the applicable transmitter would not have caused a protective shutdown in time to prevent a serious accident upon a high level trip.

Proper RETEST is another critical and often under-performed step in corrective maintenance. Management sometimes focuses excessively on 'getting the plant back up' which leads less capable and less confident techs to focus only on what is keeping the plant from running. In some cases, a quick fix may have overcome a trip or interlock hold-out situation - but the repaired or replaced part may not be performing the necessary safety, control, indication or other functions properly. Proper retest requires a strong overall skillset and proper support by applicable line management. Inadequate retest procedures are one of the most common oversights in modern industrial maintenance.

Most in the industries I work in refer to this as RCF or RCFA (Root Cause of Failure Analysis). When a tech replaces an I/P used to position a control valve it seems obvious that they should figure out what caused the failure - but this step is often skipped. Did it get water inside? Did it get clogged with rust particles or perhaps some Teflon tape or other material? Did it simply wear out from old age? These questions should be asked, and answered - and then the cause should be resolved. Some fixes may require systemic changes (such as systematically checking/changing filters or water separators, improving air systems, etc.). It makes no sense to focus only on replacing broken parts and not put effort into preventing future recurrences.