In creating integrated automated production control systems, there is an open question of simulation fidelity distribution between MES- and APC-systems according to the requirement for speed and decision-making horizon at each level. Operational planning forms a set of discrete operations organized by time and indicators. The period of the operations includes the transient and steady-state mode of the manufacturing process, but does not affect the values of transient mode indicators. Transient mode is the “noise” for operational production planning. The period of scheduled operations should be determined for petroleum refineries so that the level of the “noise” does not exceed the required production planning accuracy. The paper presents a method of calculating the transient mode parameters and the analysis results for refinery process time series, enabling us to determine the minimum operation period for the required operational production planning accuracy in the MES-system. Presents response time, average control action period and obtained estimates of transient speed on the example unit for each group of real refinery processes.