I'm not sure you are looking in the right place - the regs tells you to plan your design more or less, its not really a fault find aid.
How  big an over-voltage are you looking at and how long is its duration?

However predictable (sort of regualr) short duration over-voltages are usually related to the switching of inductive loads like motors, where all the stored energy suddenly gets 'dumped' . Less predictable but often more devastating, are currents induced by nearby (or direct !) lightning strikes. Longer duration over voltages usually relate to network faults or generator faults, where a substation transformer tap changer jams, or the neutral -earth bond fails (and up to 400V appears where 230 was expected), or on gensets problems with the regulator/ speed stabiliser, usually coupled with frequency going walk about as well....

Mike

I'm not sure you are looking in the right place - the regs tells you to plan your design more or less, its not really a fault find aid.
How  big an over-voltage are you looking at and how long is its duration?

However predictable (sort of regualr) short duration over-voltages are usually related to the switching of inductive loads like motors, where all the stored energy suddenly gets 'dumped' . Less predictable but often more devastating, are currents induced by nearby (or direct !) lightning strikes. Longer duration over voltages usually relate to network faults or generator faults, where a substation transformer tap changer jams, or the neutral -earth bond fails (and up to 400V appears where 230 was expected), or on gensets problems with the regulator/ speed stabiliser, usually coupled with frequency going walk about as well....

Mike

There's a section the the book on surge protection.