J. K. Rowling read through the script for this film, and found a line where Dumbledore mentions a girl he had a crush on when he was younger.

This was made painfully obvious to me when trying to board a train to Xi 'an at Beijing's central railway station. The security entrance to the station was, rather than a line, a crush of humanity.

On the other hand, the transient characteristics of the HVDC line fault and thus the line protections are affected by the HVDC control system, which is very complicated and still a hard nut to crush.