i dont know what hacking really is, nor a virus nor malware.
dont understand how the electric grid could be on the internet and not going to ask you to explain because it must take a long long time to explain.
Control mechanisms can be activated or deactivated via the “internet”.
Security measures have to prevent anyone from accessing those mechanisms or controllers aka computers.
Most every installation for the distribution, creation or transfer of power is vulnerable , if you can gain access to it via the WWW remotely.