1. A method of detecting an abnormal operation of a hydrocracker, comprising: collecting first data sets for the hydrocracker while the hydrocracker is in an operating region, the first data sets generated from a temperature difference variable between a first cross section in a reactor of the hydrocracker and a second cross section in the reactor of the hydrocracker in the operating region and from a load variable of the hydrocracker in the operation region; generating a regression model of the hydrocracker in the operating region using the first data sets; generating a prediction of first data generated from the temperature difference variable as a function of second data generated from the load variable using the regression model; and determining if a corresponding signal generated from the temperature difference variable deviates from the prediction of the first data generated from the temperature difference variable to detect an abnormal situation within the hydrocracker.