the ammeters. This is compared against the actual ammeter readings to determine discrepancies. Since the ammeters themselves can be faulty, for each discrepant ammeter the ammeter itself is faulty or there is at least one CB upstream that is faulty. However HyDE cannot necessarily eliminate all CBs connected to non-discrepant ammeters as candidates. For example it is possible that CB and a downstream ammeter might be both faulty resulting in the ammeter not being characterized as discrepant. HyDE uses the above heuristics to reduce the search space but in the worst case it still turns out to be exponential search. For example when looking for a 5 fault candidate, HyDE still has to eliminate all 4 fault candidates (looking for the smallest diagnosis). Some of these can be eliminated by the heuristics but the rest have to still be tested by HyDE.

The last column of Table \[table:embedding\_HyDE\] shows that problems can become intractable very quickly as one increases the number of faults and illustrates this exponential growth in the search space as a function of the number of possible faults, for instances with a fixed number of electrical components. For the problems studied, which were run on an Intel(R) 