This answer notes that while most Deep Space Network transmitters are 20 kW of power or less, one dish (DSS-43 in Canberra) is equipped with a transmitter capable of 400 kW.
As described in 101, 70-m Subnet Telecommunications Interfaces:
An additional 400-kW S-band transmitter is available at DSS-43 (Canberra) for Voyager communication and general emergency commanding. Special airspace coordination is required when using the 400-kW transmitter at a power above 100 kW, but in no case can the 400-kW transmitter be used below 17 degrees elevation, no matter what the power is. (my emphasis)
Has DSS-43 ever been used in high power mode (>>20 kW) for an emergency situation?
above: DSN's 70m antenna DSS-43 from here, one of DSN's three 70m dishes.