PLC control industry question


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Right now I am in the power generation business using PLCs. I grow more concerned about writing PLC code in systems like this as they are shipped out fast and the possible combinations for the PLC to handle is very large. The code typically has holes or product is shipped without a complete test.

As such, I am curious how other industries use PLCs. My naive vision is that although the machines may be complex, the sequence of operations is quite manageable. We constantly compete with what role the operator plays in the system. In theory, they can change breaker states, thrust the system back in auto, and it is meant to respond. I get a lot of resistance of not allowing that transition back into auto if any faults are present. Instead, most people want to just "let it ride" and see what happens. Again, my naive vision in other industries is that the machine must be placed back into a known, safe state prior to resuming.

Finally, do most of you enjoy this type of work? What are some example projects done/what other industries can I look into with PLC experience?
I do PLC programming for large show performances (I used to do amusement park ride control). We have people riding/flying on the ends of high speed winches over the stages and audience, or hydraulic control of large sections of the stage. We have to include quite a lot of redundant safety systems and everything must show a complete "Ready" state before any flight or movement can take place. Also extensive testing is done after any change to the system hardware or software. Life is almost always at risk and at a minimum a show is lost and they "walk" a house to the loss of about a million dollars (so we are told).
Wow, I didn't know PLCs were used in that area. When you say test, is it run through a set of documented test forms or is it inspected using software unit tests / validation procedures?