1. A method for the early notification of an unplanned abnormal event detection (AED) for some process units of a delayed coking unit (DCU) comprising: (a) comparing online measurements from an array of sensors for the process units to a set of models including at least two principal component analysis models for normal operation of the corresponding process units, wherein said delayed coking unit has been divided into at least two equipment groups wherein there is minimal interaction between said equipment groups and principal component analysis models correspond to equipment groups, wherein the inputs to the principal component analysis models include measurements from said array of sensors which have been divided into groups corresponding to equipment groups, wherein said equipment groups are defined by including all major material and energy integrations and quick recycles in the same equipment group and said measurements are cross-correlated with each other, (b) determining if the current operation differs from expected normal operations from the cumulative measurements of said array of sensors that are inputs to said set of models so as to detect the presence of an unplanned abnormal event condition in a process unit which has developed on a timescale of minutes to hours, and (c) determining the underlying cause of an abnormal condition in the DCU.