Why is the substation connected to the internet?
Maybe it isn't. But far better to tell the Ukrainian government that the mongo powercut it is the Russkies fault for hacking a switching station than 'fess up "It was us, we're a bunch of under-investing bunglers".
And longer term, if the government can be persuaded of this then everybody's happy: Government get to blame Russia for yet another thing, the power company will be delighted that government agree all the power infrastructure needs hardening - more money to spend and make a return on, more loot to skim or steal outright, more juicy contracts to funnel to your mates....
The only losers are the Ukrainian proles. Even the Russian's benefit, because they seem to be revelling in the status of international bag guys (if I was Putin, I certainly would be). Moving swiftly off topic, I was rather amused to see the BBC claiming that Russia was "deliberately allowing European jihadists in Syria to go free in order to bring terrorism back to the EU". If Russia carpet bombs Syria it is at fault. If it summarily executes suspected jihadis, it is at fault. If it lets them go it is at fault (apparently there's no blame on the Western nations for failing to integrate minorities, turning a blind eye when thousands of suspects "go on holiday to Turkey", and then allowing them back). And of course, Trump is Russia's fault.
I suggest we blame Russia for climate change, globalisation, poverty in Africa, drugs, and child abuse. Perhaps Mrs May should take the BBC's lead, and establish a Department of Blaming Everything on Russia.