Thermocouple assemblies for high temperature applications are provided. The thermocouple assembly includes a protection tube; and a thermocouple probe within the protection tube. The thermocouple probe includes a cable connector at a first end and extending along a longitudinal axis to a free second end. A protective housing assembly, which extends around the thermocouple probe, extends from the cable connector to a tapered end of the protective housing assembly. The protective housing assembly includes an installation unit having a fixed transition joint. An oversheath extends between the installation unit and the tapered end. The free second end of the thermocouple probe extends along the longitudinal axis beyond the tapered end of the oversheath.