Abstract: A method and system are disclosed for detecting an occurrence of an event in a target system having at least one operational variable that provides an indication of one or mine conditions of the target system which change in response to the event. The method comprises the steps of: (a) periodically calculating short and long term averages of sequentially recorded values of the operational variable, the long term average including values in addition to those included in the short term average; (b) calculating the difference between the short and long term averages; and (c) determining the occurrence of an event based upon the difference by performing a statistical evaluation selected from the group consisting of determining the significance of the difference, monitoring a particular pattern of differences, monitoring change in the differences, and combinations of two or more thereof.