Electrical engineers know the theory but lack the practical knowledge which grid form is used at your specific address (yes, here in Germany we have a few towns

Electrical engineers know the theory but lack the practical knowledge which grid form is used at your specific address (yes, here in Germany we have a few towns where one half side of a street runs TT and the other one is already migrated to TN-C or TN-C-S). An electrician specializing in lightning protection, uninterruptible power installation or in radio installations can sort out all of that far better than an engineer can.