A process for detecting an alarm in an operating machine (1), so that an operator (7) is able to interact with such a machine (1) determining a connection between the machine and the ground, comprising the steps of: determining a current value of a main parameter representative of an electric interaction between said operator (7) and said operating machine (1) under a condition of normal operation of said machine (1); comparing said determined current value with a main reference value; activating an alarm procedure as a function of said comparison. The process further comprises a starting setting step wherein said main reference value is determined, said starting setting step comprising the steps of: detecting a first reference value of said main parameter under a condition of electric insulation between said operator (7) and operating machine (1); detecting a second reference value of said main parameter under a condition of electric conduction between said operator (7) and operating machine (1); said main reference value being determined in such a manner that it is an intermediate value between said first reference value and second reference value. The invention also describes a safety system (100) for carrying out the described process and an operating machine comprising such a safety system (100).