This paper describes DINT, a data interpretation expert system which c
an provide an explanation of the real-time operating state of a substa
tion to its operators. DINT is based on a generalized version of the s
et covering model for diagnostic problem solving. This abductive reaso
ning model is an object-based, frame-like knowledge representation par
adigm. Test cases illustrate the application of the model to the real-
time operation of a substation.