Abstract: Abstract:Aiming at the tripout accident of partial 500kV output transmission lines of Togtoh Power Generation Company Limited, based on the special connection mode of auxiliary power systems of Togtoh Power Generation Company Limited and Hohhot Thermal Power Company Limited, it was proposed that after the auxiliary power system of Togtoh Power Generation Company Limited is all failure, the Hohhot Thermal Power Company Limited will appointed to provide the auxiliary power of Togtoh Power Generation Company Limited. The switching steps and the matters needing attention in the switching process were described, which are useful for safe and stable operation of the power units.

Key words: Key words:auxiliary power outage, interruption of power supply, auxiliary steam, switch over