Measurement using thermovision is part of the maintenance performed on substation equipment. Thermovision has functions to visualize and detect hot points in equipment. Thermovision work using infrared technology. Measurement using thermovision also has a weakness to find the actual temperature. This is because the emisvity value of the measured object varies between 0 to 1. This thesis discusses the validation method to test that the measurements made are accurate and precise using manual calculations and using Matlab software. Research focuses on the transformer clamp and conductors. From 66 connections, 62 connections at the terminal were in good condition and 4 connections at the terminal were in inspection while maintenance. The value of emissivity in the substation equipment is differend even though it uses 1 type of material because some factors, with an accuracy about 96.98% at transformer bay 2 , 96.44% at transformer bay 3 and 95.36% at transformer bay 4 . And the precision value is 1.98% at transformer bay 2, 1.05% at transformer bay 3 and 1.75% at transformer bay 4. The results show good accuracy and precision value, so the calculation validation test method can be used.