"We don't need no stinking fire extinguishers! In Russia we have snow!"
From Google Translate:
According to the official document, the reason for the break of the ShR insulator during shutdown is due to the freezing of the knife in the sponges and the aging of the porcelain. An additional effort was applied and it fell apart .. DZT and MTZ worked immediately, but the switching device did not trip due to a defect in the 2RP output relay, a factory defect in the coil soldering.